BACKGROUND: The Chornobyl nuclear power plant explosion in April 1986 was one of the worst ecological disasters of the 20th century. As with most disasters, its long-term mental health consequences have not been examined. AIMS: This study describes the psychological well-being and risk perceptions of exposed women 19-20 years later and the risk factors associated with mental health. METHODS: We assessed Chornobyl-related post-traumatic stress disorder (PTSD), major depressive episode (MDE) and overall distress among three groups of women in Kyiv, Ukraine (N = 797): mothers of small children evacuated to Kyiv in 1986 from the contaminated area near the plant (evacuees); mothers of their children's classmates (neighbourhood controls); and population-based controls from Kyiv. Risk perceptions and epidemiologic correlates were also obtained. RESULTS: Evacuees reported poorer well-being and more negative risk perceptions than controls. Group differences in psychological well-being remained after adjustment for epidemiologic risk factors but became non-significant when Chornobyl risk perceptions were added to the models. CONCLUSIONS: The relatively poorer psychological well-being among evacuees is largely explained by their continued concerns about the physical health risks stemming from the accident. We suggest that this is due to the long-term, non-resolvable nature of health fears associated with exposure.