Although the role of excessive efforts to exert mental control over one's unwanted intrusive thoughts has been successfully explained and documented in the cognitive-behavioural models of obsessive compulsive disorder (OCD), individual's beliefs regarding the controllability of events, that is, locus of control (LOC), have been largely ignored in recent cognitive formulations of OCD. The present study aimed to examine the relationship between these two control-related cognitions by comparing their roles in obsessive compulsive (OC) and depression symptoms. Measures of LOC, obsessive-related beliefs, depression, anxiety and OCD symptoms were administered to a sample of 530 Turkish university students. Results showed that while external LOC was positively associated with depression symptoms, the relation was different for OC symptoms. The interaction of LOC with a high desire for thought control was significantly associated with general OC symptoms, particularly with checking symptoms. The findings suggest that beliefs regarding the controllability of events are critical factors in OC symptomatology, but only when there is also a high desire of thought control.