Individuals with low Need for Cognition (NFC) have been found to process information using a peripheral route compared to individuals higher in NFC. These differences affect the formation of performance expectancies. Based on previous work demonstrating that the formation of performance expectancies can be understood as an information processing event and that inferring expectancies from the specific self-concept requires cognitive motivation, we tested whether students with higher NFC had performance expectancies in a specific subject that more strongly depended on specific self-concept. The participants (554 tenth grade students) reported their NFC, performance expectancies, general self-concept, and specific self-concepts in mathematics and English. Actual performance was assessed for mathematics. Multiple linear regressions supported the interaction-hypothesis concerning performance expectancies in mathematics and English. In addition, the higher the students' NFC, the stronger actual performance in mathematics related to the specific self-concept. The results suggested that performance expectancies mediated the effect of self-concept on performance. NFC is an important variable influencing motivational processes, and should be included in models describing the relation between self-concepts and individuals beliefs or behaviors.