The article examines theoretical and practical problems of assessing the quality of legal services caused by the absence of legally established criteria and the diversity of professional activity. It is proposed to assess the quality of legal services by comparing the terms of the contract with the course of task performance based on criteria characterizing good faith. The phased application of the criteria is justified. The author attempts to identify formal-legal criteria for quality assessment based on analysis of contractual provisions. The paper sets out concrete proposals for using the proposed method in law‑enforcement practice by courts and contracting parties when formulating quality-related provisions.