In Poland psychological assessment for the purpose of fitness-to-work certification is regulated by the law. In the majority of cases, only psychologists registered with the occupational health services are authorized to conduct the assessment procedures. In this study 32 legal documents (17 acts and 15 directives) have been analyzed to identify the most problematic issues pertaining to psychological examination and to suggest certain changes in the regulations, as well as to raise the psychologists’ awareness of the legal aspects of their work. Due to the number of the topics explored, the results of the study will be published as two separate, yet related articles. The first one concentrates on the qualifications of psychologists, the examination reference process, the aim and scope of the psychological assessment, and the validity of the assessment results. In part II other issues, not directly related to the diagnostic process, will be discussed. Med Pr 2018;69(5):561–572