Patients with hepatocellular carcinoma may manifest paraneoplastic syndromes such as hypercholesterolaemia, hypoglycaemia, hypercalcaemia and erythrocytosis. An exceptional case of hepatocellular carcinoma associated with polymyositis, a rheumatic paraneoplastic syndrome, is reported. A 72-year-old male complained for a recent muscular weakness mainly in the proximal limb muscles. The clinical course, a raised level of serum creatine kinase and electromyographic findings suggested polymyositis, and the pathological findings on muscle biopsy were compatible with this diagnosis. Computed tomography of the upper abdomen revealed a mass lesion in segment IV, V and VII of the liver, and alpha foetoprotein level was high, resulting in the diagnosis of hepatocellular carcinoma.