Previous research has shown that people with an optimistic life orientation are perceived as socially more attractive than pessimists. However, following the similarity-attraction hypothesis, we assumed that both the perceiver's and the target's life orientation affects perceptions of social attractiveness. Moreover, we were interested in how the composition of romantic partners' life orientation (similar vs. dissimilar) affects perceived relationship quality. The results of an experimental online study (N=316) confirmed previous findings: Overall, optimists were perceived as socially more attractive than pessimists. Furthermore, perceivers' life orientation moderated that effect, which was larger with optimistic than with pessimistic perceivers. Moreover, with respect to ongoing relationships optimistic participants indicated higher relationship quality if they perceived their partners as similarly optimistic. The findings are in line with the similarity-attraction hypothesis. They are discussed with regard to the benefits of optimism in social interactions and relationships.