BACKGROUND: Sleep is essential for daytime functioning and health. Given the physical symptoms of psoriasis, a higher prevalence of sleep disorders can be expected. So far, the studies examining sleep disturbance in psoriasis have been of less-than-optimal methodological quality and with mixed results. OBJECTIVES: To examine the prevalence of sleep disturbance in patients with plaque psoriasis compared with a control group, to evaluate associations with health-related quality of life (HRQoL) and examine possible disease-related predictors of disturbed sleep. METHODS: We used a cross-sectional, case-controlled design. Participants included 179 consecutively recruited patients with plaque psoriasis and 105 controls. Measures included psoriasis severity (Psoriasis Area and Severity Index); HRQoL (Dermatology Life Quality Index); insomnia severity [Insomnia Severity Index (ISI)]; sleep quality [Pittsburgh Sleep Quality Index (PSQI)]; stress (Perceived Stress Scale); itch (Itch Severity Scale); and depressive symptoms (Beck Depression Inventory). Analyses included group comparisons and regression analyses to identify predictors of sleep disturbance. RESULTS: A total of 25% of patients with psoriasis reported clinical insomnia (ISI > 15), compared with 10·5% of controls. In all, 53·6% of patients with psoriasis were poor sleepers (PSQI > 5), compared with 21·9% of controls. Itch was statistically significantly associated with all sleep-related outcomes. CONCLUSIONS: A higher proportion of patients with psoriasis experience poor sleep than controls from the general population. Itch was the main predictor of impaired sleep. Improved control of psoriasis with decreased itch may improve sleep disturbance in psoriasis.