Introduction. It is well accepted that disturbed sleep is influenced by a number of predisposing, precipitating, and perpetuating factors, and these may be biological, environmental, behavioural or psychological in nature. Personality may act as a predisposing, and potentially perpetuating factor, and literature concurs with the fact that disturbed sleep is related to increased neuroticism, internalization, anxious concerns and perfectionism. Aim of the study. To determine what maladaptive personality traits are the most frequently present among patients with disturbed sleep. Materials and methods. In this study participated 56 patients (age range 25-71 years) that have addressed themselves to the Department of Somnology from the Institute of Neurology and Neurosurgery „Diomid Gherman”. They completed the Pittsburgh Sleep Quality Index (PSQI). This self-reported instrument evaluates sleep quality for the last month and the Personality Inventory for DSM-5 (PID-5), a 220-item self-rated personality trait assessment scale for adults, that measures maladaptive personality traits. Results. From 56 patients, 35 of them (63% ) showed poor sleep quality and 21 (37%) good sleep quality. From 25 personality trait facets assessed of PID-5, higher average scores were observed in the following facets: Anxiousness (in 7% of cases), Attention Seeking (7%), Emotional Lability (7%), Hostility (7%), Intimacy Avoidance (9%), Separation insecurity (9%), Suspiciousness (9%) and Rigid Perfectionism (11%). The only trait domain detected was Negative Affect. Conclusions. The most prominent personality characteristic observed in our study is Rigid perfectionism. This may be because the maladaptive form of perfectionism includes concern over mistakes and excessively high personal standards and is associated with worry and rumination. Worry and rumination at bedtime are, in turn, assumed to lead to sleep onset and sleep maintenance difficulties. The predominant domain of Negative Affect detected in our study shows that people with sleep complain have frequent and intense experiences of a wide range of negative emotions: instability of emotional experiences and mood, feelings of nervousness, tenseness, fears of being alone due to rejection, frequent angry feelings, feelings of being mistreated, avoidance of interpersonal attachments. These outcomes provide objective support for further analytical studies in order to find out if there is a significant difference between good sleepers and bad sleepers in correlation with these personality traits.