Satisfaction of a customer or client, whether that of a commercial organization or a public administration unit, is nowadays regarded to be a priority. Hence the need to measure customer satisfaction, and perform the measurement in a way which yields accurate result. This can be accomplished by using reliable and valid measurement instruments. In the article the authors presented the process of validation of the proposed scale for measuring the service satisfaction level of 'client' of the public administration unit. The empirical part of the article is preceded by an overview of the theory underlying the concepts of satisfaction and its measurement, customer service quality, as well as validity and reliability of a scale. As a result, the satisfaction measurement scale is presented which satisfies the requirements of validity and reliability.