There is a long debate over the superiority of performance-only measures vs. performance-expectation measures of service quality. This paper analytically derives the superiority conditions of the measures in predicting customer satisfaction. The conditions show that the superiority of the measures is determined by two factors. One is the strengths of linkages between the constructs (expectation, performance, and customer satisfaction) in the customer satisfaction formation process, and the other is customer heterogeneity in the evaluation of constructs in the process. The source of customer heterogeneity implies that the superiority is affected by the procedure for measuring service quality because the degree of customer heterogeneity in the evaluation of perceived and expected service quality may vary according to the measurement procedure.