Psoriasis is a chronic relapsing autoimmune disease with a multigenetic predisposition, which occurs in about 2% of patients in Croatia and shows variable occurrence in the world. Psoriasis can be associated with various diseases, including autoimmune diseases (pemphigus, pemphigoid, vitiligo), and slightly less with allergic diseases (atopic dermatitis, asthma, urticaria, allergic contact dermatitis). According to clinical manifestations, psoriasis appears as plaque psoriasis, erythrodermic form and pustular psoriasis. Provocative factors that encourage psoriasis are infections, endogenous factors, hypocalcemia, psychogenic factors and medications. Psoriasis may worsen other dermatoses such as contact dermatitis, inflammatory dermatoses and skin cancer, and the association of psoriasis with internal diseases is quite common (HIV, Crohn's disease, liver lesions, vascular diseases, amyloidosis and gout). Today, psoriasis is considered as a systemic inflammatory disease that can also affect the joints. Atypical localization of psoriasis, as well as resistant cases of psoriasis and other papulosquamous and eczematoid dermatoses require detailed work-up and confirming of diagnosis because of the possibility of the existence of other diseases. This paper discusses the association of psoriasis with rheumatic and other internal diseases.