This paper describes research on the perceived impact of process improvement activities on the quality of the services provided to the (internal) customers. A questionnaire was developed to map the notion 'quality of service' from the point of view from both IT-departments and business customers. These assessments were measures against a subjective scale that runs from 'insufficient' to 'sufficient'. This survey was used in 9 different IT-development organisations, all part of the same holding. On the basis of the internal report on this survey top-management accepted those SPI-investments were providing sufficient benefits and required a repeat at one-year intervals.