With the growing body of research confirming the importance of metacognition in the academic context, it is becoming increasingly important to study factors that contribute to this ability. While the research efforts centered around the metacognitive calibration outline cognitive traits that can account for the interindividual differences in self-assessment, there hasn't been much research regarding non-cognitive traits that might be significant in this context. Thus, this research focuses on three groups of such traits – personality traits as defined by the Big Five model, subjective well-being and gender. This study was conducted on a student sample from Croatia. The participants were presented with an abstract reasoning test, Esoteric Analogies Test (EAT), where they had to indicate both the correct answer to each question and their confidence level, a personality trait questionnaire Big Five Inventory (BFI), Ryff's Scales of Psychological Well-being (RSPWB) and a short list of demographic questions. The analysis has shown that the only personality trait predictive for the task performance self-evaluation was neuroticism, which yielded a negative correlation with the confidence in one own's answers. On the other hand, the subjective well-being facets - autonomy, environmental mastery, personal growth, and self-acceptance were all positively correlated to the task performance confidence levels. The mediation effect of subjective well-being on the relation between personality traits and confidence levels wasn't observed. Finally, men were more confident in the correctness of their solutions than women, even though there was no difference in their overall test score. All the effects were small in size.