Patientswith obsessivecompulsivedisorder(OCD)with and withouta historyof motortics maybe distinguishedbasedontheirclinicalfeatures andcouldconstitutedifferentsubtypesofOCD(McDougle,1993;Zohar, 1997).The presentstudysoughtto identifydifferencesin the regional cerebrrdbIoodflow(rCBF)in OCDpatientswithandwithoutcbmnictic disorder.Twen~-sevenpatientswith OCD,includingsevenwith associatedsimplechronicmotortic disorder,as definedby the DSM-IVand ICD-10,and sixteenage, sex and handednessmatchedhealthycontrols, were studied at rest usirrga high resolutionsingle photon emission computerizedtomography(SPECT)scan and 99mTc-HMPAOas the tracer.The rCBFof 14regionsof interestwas manuallytracedon each individualscan and quantifiedas a percentageof the mean cerebella uptake.SeverityofOCD,anxietyanddepressivesymptomsandpresence of motortics were assessedby the Y-BOCS,HRS-D,HRS-A,MADRS andYale GlobalTics Severi~ Scale.PatientswithOCDandassociated chronictic disordershowedan increasedrf2BFin rightcaudatenucleus comparedto OCD patientswithouttics (C)CDwith tics= 0.96; OCD withouttics= 0.92;p= O.009).OCDpatientswithchronictics sIso had lower severity of obsessive-compulsivesymptoms(global Y-BOCS score),particularlyin the obsessivesymptomssubscale.Thesefindings showingdifferentclinicalfeaturesandrCBFpatternssupportthe notion that OCDwithconcurrentchronictic disordermayconstitutea specific subtypeof OCD.