Introduction Cognitive impairment in chronic diseases such as psoriasis is an increasing clinical challenge. Objective To assess the frequency and extent of difficulties in cognitive functioning in people with psoriasis compared to healthy people. Patients and methods The systematic review was carried out on the 23rd July, 2021 by two trained psychologists resulting in a selection of 11 studies on 971 patients with psoriasis and 10,242 controls. Results A review of the studies showed irregularities in many cognitive domains, including working memory processes, executive functions, long-term verbal memory, attention, and the visuospatial domain. Depending on the methods used to assess cognitive dysfunctions and the characteristics of patients in different studies, large differences in the frequency of cognitive impairment in patients with psoriasis were observed, ranging from 0 to 91.9%. Conclusions The authors conclude that there is a need for longitudinal studies to identify factors important for the development and persistence of cognitive impairment in psoriatic patients.