In this research, the contributions of styles of attachment, irrational beliefs and psychological symptoms to the prediction of cognitive flexibility were analysed. The sample consists of 436 students studying in various departments and faculties in Mersin University. The Cognitive Flexibility Scale, Relationships Scale, Irrational Beliefs Scale and Short Symptom Inventory were applied. Multiple-regression analysis and stepwise regression analysis were used to analyse the data. According to the results of the research, it was found out that all of the independent variables explained approximately 41% per cent of the cognitive flexibility; according to the stepwise regression analysis, it was found out that the students' cognitive flexibility was predicted most by the variables of irrational beliefs, obsessive attachment and anxiety.