Having knowledge about the impact of an intervention on a client in a specific psychotherapy session helps us to examine whether the process is helpful, effective or harmful. Also the agreement levels between therapist and client for the session assessment effect the important decisions respecting planning and changing the psychotherapy process. The main aim of this study is investigating the session impact in the context of therapist-client relationship. Accordingly, the targets of this study are a) examining the psychometric properties and factor structure of Session Evaluation Questionnarie, b) evaluating the agreement levels about session impact between therapists and clients, c) exploring the main indicator of session impact for clients and therapists. 69 therapists and 112 clients participated in the study and the analysis were conducted from the data which were obtained from 810 sessions. The results of exploratory factor analysis indicated that the binary factor structure of the questionnaire was supported and the reliability of the dimensions were quite high (Cronbach a = .87 - .92). At the same time, the results refered that there were a significant agreement between therapists and clients for all items and dimensions (ICC Mean = .45). Moreover, the results of multiple group analyses showed that the models of therapist and client were overlapped with each other in terms of the questionnaire's binary structure. Rather than 'smoothness', the 'depth' dimension was the main indicator of the session impact for both therapists and clients. With this study, the 'session impact' which is an important and efficacious variable for psychotherapy processes was investigated for the first time in Turkey with therapist-client dyads. [ABSTRACT FROM AUTHOR]