diff --git a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2SelectionParseTest.java b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2SelectionParseTest.java
index 040b0702884..9897677cabf 100644
--- a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2SelectionParseTest.java
+++ b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2SelectionParseTest.java
@@ -37,6 +37,7 @@ import org.eclipse.cdt.core.dom.ast.cpp.ICPPField;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPMethod;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPNamespace;
 import org.eclipse.cdt.core.parser.ParserLanguage;
+import org.eclipse.cdt.internal.core.dom.parser.ASTNode;
 
 /**
  * @author dsteffle
@@ -1510,6 +1511,54 @@ public class AST2SelectionParseTest extends AST2SelectionParseBaseTest {
 		assertTrue(name.resolveBinding() instanceof IVariable);
 	}
 	
+	public void testBug86870() throws Exception {
+		StringBuffer buffer = new StringBuffer();
+		buffer.append("#if VERSION == 1\r\n"); //$NON-NLS-1$
+		buffer.append("#define INCFILE \"vers1.h\"\r\n"); //$NON-NLS-1$
+		buffer.append("#elif VERSION == 2\r\n"); //$NON-NLS-1$
+		buffer.append("#define INCFILE \"vers2.h\" /* and so on */\r\n"); //$NON-NLS-1$
+		buffer.append("#else\r\n"); //$NON-NLS-1$
+		buffer.append("#define INCFILE \"versN.h\"\r\n"); //$NON-NLS-1$
+		buffer.append("#endif\r\n"); //$NON-NLS-1$
+		
+		String code = buffer.toString();
+		int offset1 = code.indexOf( "#if VERSION == 1" ); //$NON-NLS-1$
+		int length = "#if VERSION == 1".length(); //$NON-NLS-1$
+		IASTNode node = parse( code, ParserLanguage.C, offset1, length );
+		assertNotNull(node);
+		assertEquals( ((ASTNode)node).getLength(), length);
+		
+		offset1 = code.indexOf( "#elif VERSION == 2" ); //$NON-NLS-1$
+		length = "#elif VERSION == 2".length(); //$NON-NLS-1$
+		node = parse( code, ParserLanguage.C, offset1, length );
+		assertNotNull(node);
+		assertEquals( ((ASTNode)node).getLength(), length);
+		
+		offset1 = code.indexOf( "#else" ); //$NON-NLS-1$
+		length = "#else".length(); //$NON-NLS-1$
+		node = parse( code, ParserLanguage.C, offset1, length );
+		assertNotNull(node);
+		assertEquals( ((ASTNode)node).getLength(), length);
+
+		offset1 = code.indexOf( "#define INCFILE \"versN.h\"" ); //$NON-NLS-1$
+		length = "#define INCFILE \"versN.h\"".length(); //$NON-NLS-1$
+		node = parse( code, ParserLanguage.C, offset1, length );
+		assertNotNull(node);
+		assertEquals( ((ASTNode)node).getLength(), length);
+		
+		offset1 = code.indexOf( "INCFILE \"versN.h\"" ); //$NON-NLS-1$
+		length = "INCFILE".length(); //$NON-NLS-1$
+		node = parse( code, ParserLanguage.C, offset1, length );
+		assertNotNull(node);
+		assertEquals( ((ASTNode)node).getLength(), length);
+		
+		offset1 = code.indexOf( "#endif" ); //$NON-NLS-1$
+		length = "#endif".length(); //$NON-NLS-1$
+		node = parse( code, ParserLanguage.C, offset1, length );
+		assertNotNull(node);
+		assertEquals( ((ASTNode)node).getLength(), length);
+	}
+		
 	public void testBug87179() throws Exception
 	{
 		StringBuffer buffer = new StringBuffer();
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/parser/scanner2/BaseScanner.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/parser/scanner2/BaseScanner.java
index 7cc9d369308..81f83c286b6 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/parser/scanner2/BaseScanner.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/parser/scanner2/BaseScanner.java
@@ -2583,6 +2583,9 @@ abstract class BaseScanner implements IScanner {
                         handleCompletionOnExpression(CharArrayUtils.extract(
                                 buffer, start, len));
                     branchState(BRANCH_IF);
+                    
+                    processIf(pos, pos + start + len, true); // fix 86870, process IF before skipping the condition and only process it once
+                    
                     if (expressionEvaluator.evaluate(buffer, start, len,
                             definitions,
                             getLineNumber(bufferPos[bufferStackPos]),
@@ -2590,9 +2593,7 @@ abstract class BaseScanner implements IScanner {
                         skipOverConditionalCode(true);
                         if (isLimitReached())
                             handleInvalidCompletion();
-                        processIf(pos, bufferPos[bufferStackPos], true);
                     }
-                    processIf(pos, bufferPos[bufferStackPos], false);
                     return;
                 case ppElse:
                 case ppElif:
@@ -3406,11 +3407,11 @@ abstract class BaseScanner implements IScanner {
                                 skipToNewLine();
                                 if (checkelse && nesting == 0) {
                                     processElse(startPos,
-                                            bufferPos[bufferStackPos] + 1, true);
+                                            bufferPos[bufferStackPos], true);
                                     return;
                                 }
                                 processElse(startPos,
-                                        bufferPos[bufferStackPos] + 1, false);
+                                        bufferPos[bufferStackPos], false);
                             } else {
                                 //problem, ignore this one.
                                 handleProblem(
@@ -3435,16 +3436,16 @@ abstract class BaseScanner implements IScanner {
                                                     definitions,
                                                     getLineNumber(bufferPos[bufferStackPos]),
                                                     getCurrentFilename()) != 0) {
-                                        // condition passed, we're good
-                                        processElsif(start,
+										// condition passed, we're good
+                                        processElsif(startPos,
                                                 bufferPos[bufferStackPos], true);
                                         return;
                                     }
-                                    processElsif(start,
+                                    processElsif(startPos,
                                             bufferPos[bufferStackPos], false);
                                 } else {
                                     skipToNewLine();
-                                    processElsif(start,
+                                    processElsif(startPos,
                                             bufferPos[bufferStackPos], false);
                                 }
                             } else {
@@ -3890,7 +3891,7 @@ abstract class BaseScanner implements IScanner {
                     break;
                 } else if (!escaped && bufferPos[bufferStackPos] < limit
                         && buffer[bufferPos[bufferStackPos] + 1] == '\n') {
-                    bufferPos[bufferStackPos]++;
+//                    bufferPos[bufferStackPos]++;  // Do not want to skip past the \r
                     return;
                 }
                 break;