Psoriasis is an immune-mediated inflammatory disease, which, in studies among adults, have been shown to cluster with autoimmune disease. The aim of this cross-sectional register study was to examine possible associations between 9 pre-selected autoimmune diseases and psoriasis in children and adolescents. The study population consisted of all individuals living in Denmark, age under 18 years on 31 December 2012. A total of 1,925 children and adolescents with psoriasis and 1,194,712 without psoriasis were identified. Psoriatic arthritis (adjusted odds ratio (OR) 10.08; 7.97-12.74), rheumatoid arthritis (adjusted OR 6.61; 2.75-15.87) and vitiligo (adjusted OR 4.76; 1.71-13.20) showed strong associations with psoriasis. In addition to increased risk of selected autoimmune diseases, the presence of psoriasis was associated with increased risk of multiple concurrent autoimmune diseases compared with children and adolescents with-out psoriasis. Clinicians should be aware of extracutaneous symptoms when treating children and adole-scents with psoriasis.