This thesis aimed to investigate the relationship between obsessive-compulsive symptoms (particularly obsessive intrusive thoughts) and executive functions (particularly working memory). Previous research had demonstrated executive function (EF) deficits in individuals with OCD. Executive functions are those cognitive mechanisms that help to control and regulate thoughts and behaviour. However, several questions remained unanswered: 1) do individuals with subclinical OCD also demonstrate EF deficits? 2) Are those EF deficits found in individuals with OCD trait in nature, or caused by state factors? 3) Are EFs implicated in OCD-relevant processes, such as thought control strategies? Three studies were conducted to help investigate these questions further. The study presented in chapter two found no difference between individuals with subclinical OCD and nonclinical individuals on a range of executive function tasks. The study presented in chapter three found that an increase in obsessive intrusive thoughts did not lead to impairments in working memory. The study presented in chapter four found no relationship between working memory and an individual’s ability to dismiss obsessive intrusive thoughts. The implications of the results from this thesis are discussed and future directions are suggested.