Objective: cognitive models of OCD proposed that inflated responsibility/threat, importance/control of thought, and perfectionism/certainly are a vulnerability and maintenance cognitive factors specific to OCD symptoms. Attachment theory assumed that those cognitive factors are obsessive beliefs that can be explained within a family-attachment relationship. Although several studies have been conducted on the specificity of cognitive factors and family–attachment relative to OCD, a meta-analysis on this issue does not exist yet. Using meta-analytic techniques, the current study summarized cross-sectional data to examine: (a) which stronger predictors are related to OCD symptoms in clinical and non-clinical samples. Method: Online databases were searched. Cross-sectional studies were included if they (a)assessed OCD symptoms in clinical or non-clinical samples, (b) reported correlations or between-groups data (predictors of OCD symptoms). Seventeen studies (n= 6238) were included in random-effect meta-analyses. Results: Effect size on relation of predictors to OCD symptoms was medium. predictors were strongly associated with OCD symptoms [r= 0.456, p=.0001],   Conclusions: Using meta-analytic technique, the current study examined predictors of obsessive - compulsive disorder, and it revealed that cognitive factors such as “inflated responsibility/threat, importance/control of thought, and perfectionism/certainly “and family- attachment are predictors of OCD.