In services research, little attention has been devoted to long-term intrinsic personality traits. Long-term personality traits predict short-term affective states and thus understanding them is important from a service standpoint. Further, identifying long-term personality traits facilitates the targeting of customers who are predisposed to evaluate services in a positive manner. This study focuses on one long-term affective trait, happiness, and examines its impact on service evaluation and commitment, as it has been shown that the level of happiness affects whether people perceive life events, both great and small, in a positive or negative manner. Three studies were conducted to research the issue. The first study shows that customers who are happier evaluate service quality in utilitarian services in a more positive manner than do customers who are less happy. The second study shows that for hedonic services, involvement serves as an antecedent to perceived service quality; happier customers are also more involved in hedonic services, and thus perceive service quality in a more positive manner. Study 3 examines the link between happiness and commitment and shows that customers who are happier are also more prone to be committed to hedonic services. These results contribute to the marketing literature by showing that customers are predisposed to evaluate service quality in line with their level of happiness in the case of both utilitarian and hedonic services. Thus, marketing scholars and practitioners ought to recognize that service quality and commitment are partially predetermined by the personality of the customer and that some customers are more difficult to please than others. © 2011 Wiley Periodicals, Inc.