According to self-report questionnaire studies, insomnia patients differ from healthy controls with respect to several personality traits. The current study aimed at exploring how these personality traits may translate into behavior. Insomnia patients' behavior during psychometric testing (n = 163) was investigated in comparison to healthy controls (n = 81), patients with other sleep disorders (n = 80), and patients with obsessive-compulsive disorder (n = 36). In line with our hypotheses, insomnia patients made more additional comments than healthy controls and more corrections than patients with other sleep disorders during sleep-related questionnaire completion. Furthermore, insomnia patients calculated the sum score of a depression questionnaire more frequently than both healthy controls and patients with other sleep disorders. These findings further support the assumption of an altered personality profile in patients with primary insomnia. Future work should aim to elucidate what personality factors these novel behavioral markers may reflect.