Aim. The research was aimed at establishing which qualities of therapists and patients influence the therapists' interpersonal skills as well as whether therapists' interpersonal skills as perceived by patients correlate with the effectiveness of individual therapy measured by such indicators as the level of life satisfaction (subjective index) and the number of symptoms of mental disorders (objective index). Therapists were tested with regard to their professional qualifications and work experience, while patients were examined in terms of the type of mental disorder and the level of commitment to achieve change. The orientation and length of individual therapy were also taken into account. Method. A purposive sampling was applied, including such criteria as: kind of psychotherapeutic approach, type of mental disorder and also the number of sessions. 40 patients and their therapists were tested by means of the following research instruments: The Relationship Questionnaire (Truax, 1977), The Satisfaction with Life Scale (Diener et al., 2001), The General Health Questionnaire 28 (Goldberg, 2001), The Therapy Involvement Scale and The Therapists' Professional Competencies Questionnaire developed by Szymczyk (2006). Results. Patients of both licensed and non-licensed therapists perceive a strong connection between the level of therapists' empathy and the effects of therapy. Patients participating in eclectic and humanistic-existential therapy indicate correlations between therapists' warmth and achieved change. Patients with personality disorders point at a strong correlations between the therapists' empathy and the increase of life satisfaction, as well as the decrease of symptoms of mental disorders. Patients with anxiety disorders indicate the importance of warmth, which correlates with lower symptoms of depression. The fewest correlations were observed between therapists' genuineness, as assessed by patients, and psychotherapy outcomes.