Introduction: Patients with psoriasis have increased risk of cardiovascular disease, but data on atopic dermatitis (AD) are less clear-cut. However, it is well-established that erectile dysfunction (ED) can serve as a risk marker for coronary disease. Aim: To investigate the incidence, prevalence, and risk of ED in men with psoriasis and AD. Methods: The sample included all Danish men at least 30 years old. In patients with AD and psoriasis, we determined disease severity based on use of systemic therapy. We performed a cross-sectional study (January 1, 2008) using logistic regression to estimate the prevalence and odds ratio of ED. Moreover, in a cohort study design, patients were followed from January 1, 2008 through December 31, 2012, and Cox regression models were used to estimate adjusted hazard ratios of new-onset ED. Models were adjusted for potential confounding factors, including age, socioeconomic status, health care consumption, smoking, alcohol abuse, diabetes, and cholesterol-lowering drug use. Main Outcome Measures: The outcome was initiation of pharmacotherapy used for treatment of ED. Results: The sample consisted of 1,756,679 Danish men (age range = 30-100 years), of which 2,373 and 26,536 had adult AD (mild = 1,072; severe = 1,301) and psoriasis (mild = 21,775; severe = 4,761), respectively. Mean ages (SDs) were 53.0 (14.6), 46.7 (12.0), and 56.3 (13.8) years for the general population, patients with AD, and patients with psoriasis, respectively. Prevalences of ED were 8.7%, 6.7%, and 12.8% for the general population, patients with AD, and patients with psoriasis, respectively. Adjusted odds ratios (logistic regression) of ED were decreased in patients with AD (0.68; 0.57-0.80) but increased in those with psoriasis (1.15; 1.11-1.20). Adjusted odds ratios for mild and severe AD were 0.63 (0.48-0.82) and 0.72 (0.58-0.88), respectively, and those for psoriasis these were 1.16 (1.11-1.21) and 1.13 (1.03-1.23). Adjusted hazard ratios (Cox regression) were 0.92 (0.76-1.11) for AD and 1.14 (1.08-1.20) for psoriasis. The ED risk was not increased in men with mild AD (0.85; 0.63-1.14) or severe AD (0.97; 0.76-1.24) but was significantly increased in men with mild psoriasis (1.13; 1.09-1.20) and severe psoriasis (1.17; 1.04-1.32). Conclusion: We found an increased prevalence and risk of ED in men with psoriasis, whereas the risk was comparable to (and even slightly lower than) the general population for men with AD. Copyright (C) 2016, International Society for Sexual Medicine. Published by Elsevier Inc. All rights reserved.