Summary Background Psoriasis is a chronic inflammatory disease associated with an increased cardiovascular risk. Metabolic syndrome is a significant predictor of cardiovascular events. Objective To investigate the prevalence of metabolic syndrome in patients with psoriasis. Methods We performed a hospital-based case–control study on 338 adult patients with chronic plaque psoriasis and 334 patients with skin diseases other than psoriasis. Results Metabolic syndrome was significantly more common in psoriatic patients than in controls (30·1% vs. 20·6%, odds ratio 1·65, 95% confidence interval 1·16–2·35; P = 0·005) after the age of 40 years. Psoriatic patients also had a higher prevalence of hypertriglyceridaemia and abdominal obesity, whereas hyperglycaemia, arterial hypertension and high-density lipoprotein cholesterol plasma levels were similar. Although psoriasis patients were more frequently smokers, the association of psoriasis with metabolic syndrome was independent from smoking. There was no correlation between severity of psoriasis and prevalence of metabolic syndrome. Psoriatic patients with metabolic syndrome were older and had a longer disease duration compared with psoriatic patients without metabolic syndrome. Conclusion Psoriatic patients have a higher prevalence of metabolic syndrome, which can favour cardiovascular events. We suggest psoriatic patients should be encouraged to correct aggressively their modifiable cardiovascular risk factors.