Objective Toanalysisandcomparison MRImanifestationsofthepigmentedvillonodularsynovitis(PVNS)andgiant celltumoroftendonsheath(GCTTS),andfurthertoimprovethediagnosticaccuracyofthem.Methods 10patientswithPVNSand 20patientswithGCTTSconfirmedbyoperationandpathologywereanalyzedretrospectively.Allpatientswereexaminedwith MRI. Results Among10casesofPVNS,8caseswerelocatedinkneejoint,2infoot.5casesshoweddiffuseform,othersshowedfocal form.Comparedwiththesignalofskeletalmuscle,theproliferativesynovialappearedasisointensityonT1WI,mainlyisointensityor slighthyperintensityonT2WI.NodularhypointensityofT1andT2signalwereseenwithinthesynovialmembrane.Among20casesof GCTTS,18werelocalizedlesions,2werediffuselesions.Therewere3casesinkneejoint,8casesinhandsandfeetrespectively,1case inshoulderjoint.Among20casesofGCTTS,11caseswerenodularlesions,9caseswereirregularGshaped.Thelumpsappearedas isointensityorhypointensityonT1WI,andmostofthem wereslighthypointensityonT2WI.Conclusion The MRIsignalofPVNS andGCTTShaveoverlappinganddifference.Thelocation,morphologyoflesionscombinedwith MRIfindingscanimprovethediagnostic accuracyofthem.