Since its introduction into the marketing literature by Martilla and James, the Importance-Performance Analysis has proven multiple times to be a cost-effective technique for measuring attribute importance and performance of services for the customer. Additionally, it gives managers valuable hints in order to improve their products and services. However, despite a long list of successful applications overtime one critical aspect remains—the validation of the importance values by direct measurement. Besides the limitations and critics that accompanied with stated importance techniques, a lot of research results show that it is better to use direct methods in place of indirect measures. Some researchers suggest measuring the customers’ priority structure to compensate the critical points within the direct questioning. This study shows how the critical incident technique can be helpful for the validation of such results.