ABSTRACT BACKGROUND: Instant messaging services (IMS) are widely used in medical practice. OBJECTIVE: To evaluate perceptions regarding use and usability of IMS within clinical practice and assess users’ knowledge of the ethical and legal context involved in using IMS within medical practice. DESIGN AND SETTING: Cross-sectional study conducted in different hospitals and medical institutions in Minas Gerais, Brazil. METHODS: Medical students, medical residents, primary care physicians and specialist doctors answered an online questionnaire regarding epidemiological data, graduation level and use of IMS for medical communication. Responses were collected over a five-month period and data were assessed using the IBM-SPSS software. RESULTS: 484 people answered the questionnaire: 97.0% declared that they were using IMS for medical-related purposes; 42.0%, to elucidate medical concerns every week; 75.0%, to share imaging or laboratory tests and patients’ medical records; and 90.5%, to participate in clinical case-study private groups. Moreover, only 37.0% declared that they had knowledge of the legislative aspects of use of smartphones within clinical practice. Differences in the frequency of discussion of medical concerns within the daily routine between student/residents and general practitioners/specialists, and in the frequency of image-sharing and patient-guiding/assistance between students and medical doctors, were observed. CONCLUSIONS: Our results provide reliable proof that medical doctors and students use IMS, as a tool for clinical case discussions, interactions between healthcare providers and patients, or dissemination of knowledge and information. Nonetheless, because of limitations to the ethical and legal regulations, evidence-based discussions between authorities, academics and medical institutions are needed in order to fully achieve positive outcomes from such platforms.