A closer look at the extant literature of service research reveals an ongoing debate about the relative importance of process value over outcome value in the assessment of service delivery. This study advances this literature by investigating and comparing the effects of process value and outcome value on affective and cognitive relationship strength. From the analysis of a sample including178 customers of a large transportation and logistics company, the results demonstrate that process value imposes a larger effect on both affective and cognitive relationship strength than that of outcome value. Furthermore, cognitive strength is a stronger determinant of both attitudinal and behavioral loyaltyof customersthan affective strength.From these findings, some important implications have been drawn for managers, which help them to invest more effectively into customer relationships and turn these relationships into sustainable loyalty