A large body of research focuses on the (socio)economic antecedents of marriage dissolution. Less is known about the factors that affect the stability of cohabitations. The focus in this study, which is based on Finnish register data, is on whether the socioeconomic resources of the partners affect the stability of cohabitations and marriages in a similar way. According to the results, a lower level of education, unemployment (of the man in particular) and the male partner's (or the couple's) low income increased dissolution rates in unions of both types. The stabilizing effects of each partner's high educational level as well as the male partner's employment and high income were stronger in marriages. The union types also seemed to differ in that the separation-promoting effect of the female partner's high (absolute or relative) income was stronger in marriages, but high-income women are few and the interactions between union type and the income of the female partner were statistically insignificant. The overall conclusion is that in the Finnish context, the socioeconomic antecedents of union dissolution are remarkably similar in cohabitations and marriages, but socioeconomic resources are somewhat more important for the stability of marriages. Only weak support was found for the idea that cohabitations are more compatible with income equality. © 2012 Springer Science+Business Media Dordrecht.