The coexistence of systemic lupus erythematosus (SLE) and psoriasis is rarely observed in everyday clinical practice. Apart from providing a correct diagnosis, a major difficulty is to provide a proper treatment. In this case, for example, the use of systemic glucocorticosteroids may have a negative effect on the course of psoriasis, whereas phototherapy, which is widely practiced in psoriasis, may cause SLE exacerbation. The aim of the paper is to present the difficulty along the diagnostic process and in choosing the best type of treatment for patients with a coexistence of SLE and psoriasis and also a review of the subject-related literature.