Introduction: When evaluating gender differences in mental disorders and suicidality, specifically between European countries, studies are sparse and frequently hindered by methodological issues, such as the limited items evaluated and inconsistent sampling designs. Methods: In ten European countries participating in the World Mental Health Survey Initiative, lifetime internalizing and externalizing disorders and suicidality were assessed among 37,289 respondents. Disorders were classified using DMS-IV criteria. Odds ratios (OR) for gender differences were calculated using logistic regression, while trends across age-groups were tested via gender × age interaction. Results: Within countries, prevalence of any lifetime internalizing disorder ranged from 10.8% to 44.5% among women and 5.9% to 26.5% among men, with women having consistently higher odds than men (OR range: 1.52-2.73). Prevalence of any lifetime externalizing disorders ranged from 0.2% to 6.6% among women and 2.2% to 22.4% among men, with women having consistently lower odds than men (OR range: 0.05-0.35). Any lifetime suicide attempt was found in 0.8-5.4% of women and 0.3-2.4% of men, showing inconsistent relative gender-differences across countries (OR range: 0.77-4.72). Significant effects in gender OR across age-groups were not observed for any internalizing disorder or suicide attempt, yet were present for any externalizing disorder in France (p = 0.01), the Netherlands (p = 0.05), and Spain (p = 0.02). Limitations: Mental disorders were assessed with the CIDI 3.0 and not psychiatric evaluations. Suicidality does not fully represent more important clinical events, such as suicide mortality. Conclusions: Consistent across European countries, internalizing disorders are more common among women and externalizing disorders among men, whereas gender differences in suicidality varied.