Introduction: Survival in patients with cyanotic congenital heart disease (CCHD) has improved dramatically. The result is an ageing population with risk of acquired heart disease. Previous small uncontrolled studies suggested that these patients are protected against the development of atherosclerosis. To test this hypothesis, we sought to determine the prevalence of subclinical atherosclerosis in a larger population of patients with CCHD. Method: We compared the prevalence of subclinical atherosclerosis in adult CCHD patients from Denmark, Sweden, Norway and Australia, with that in age-, sex-, smoking status-, and body mass index matched controls. Coronary artery atherosclerosis was assessed on computed tomography with coronary artery calcification (CAC) score. Subclinical atherosclerosis was defined by CAC-score > 0. Carotid artery atherosclerosis was evaluated using ultrasound by measuring carotid plaque thickness (cPT-max) and carotid intima media thickness (CIMT). Lipid status was evaluated as an important atherosclerotic risk factor. Results: Seventy-four patients with CCHD (57% women, median age 49.5 years) and 74 matched controls (57% women, median age 50.0 years) were included. There were no differences between the groups in: CAC-score > 0 (21% vs. 19%, respectively; p = 0.8), carotid plaques (19% vs. 9%, respectively; p = 0.1), cPT-max (2.3 mm vs. 23 mm, respectively; p = 0.1) or CIMT (0.61 mm vs. 0.61 mm, respectively; p = 0.98). And further no significant differences in lipoprotein concentrations measured by ultracentrifugation. Conclusion: Young adults with CCHD have similar cardiovascular risk factor profiles and measures of subclinical atherosclerosis, compared with controls. Given their increasing life expectancies, athero-preventive strategies should be an important part of their clinical management. (C) 2018 Elsevier B.V. All rights reserved.