Introduction: Idiopathic inflammatory myopathies are systemic autoimmune diseases characterized by progressive proximal muscle weakness. Cancer-associated myositis represents the worst prognostic group within this heterogeneous disease. Aim: The aim of this study was to reveal factors which increase the risk factors for association of cancerous disease in patients with myositis. Furthermore, the authors explored the most common types of associated malignancies in their patients with myositis and characterize the clinical findings in a sub-group of anti-p155/140 positive patients. Method: In this retrospective study, myositis patients with and without associated cancer were analysed (32 and 64 patients, respectively). In addition, anti-p155/140 positive and negative groups were compared, irrespective to the presence of associated malignancies. Results: The risk for associated malignancy was higher in patients with severe muscle and skin symptoms and those with dermatomyositis. Furthermore, increased risk for malignancy was noted in the presence of particular skin symptoms and the absence of systemic symptoms. The anti-p155/140 antibody was proved to be a feasible marker of an independent clinical sub-group which overlapped clinical characteristics with cancer-associated myositis. Conclusions: These results may help the identification of patients with myositis with a higher risk for associated malignancy. Orv. Hetil., 2014, 155(36), 1437–1444.