Prior studies have found that sexual activity relates to relationship happiness and stability, but little research has examined the role of partnership type in sexual expression. This paper brings together the demographic and sexuality literature regarding the changing nature of intimate partnerships, and investigates how emotional connection, compatibility between partners in terms of their sexual interest and sexual preferences, and relationship happiness compare across three types of partnership: living apart together, cohabitation and marriage. Regression models of data from the British National Study of Sexual Attitudes and Lifestyles suggest that for both men and women compatibility in sexual interest and relationship happiness differ by partnership status: those living apart together report more similar sexual interest as their partners than married individuals, but are less happy in their relationship. Cohabiting men and women are similar to married individuals in their sexual expression, but report lower levels of relationship happiness. This study brings a distinct approach to the demographic research on partnership differences.