Introduction. The key element of successful treatment of gestational diabetes mellitus (GDM) is a well-organized diet and physical activity plan for the patient. In order to better monitor everyday life activity of patients and get more well-formed information on the process of treatment, a mobile application with electronic diary was given to patients at Almazov Federal North-West Medical Research Centre. The aim — of the study is to assess the beneficial action of mHealth app diary usage in clinical practice of gestational diabetes treatment. Material and methods. Android application diaCompanion was developed and given to a group of patients with detected GDM, who used it to keep records of food intake, blood glucose measurements, insulin injections, physical activity, sleep and ketones. These records were formed into unified electronic diaries and sent remotely to attending physicians. The developed diary app contained necessary functionality for disease management, including embedded food database with micronutrient and macronutrient parameters for more than 2000 local food items, record analysis and editing, database management, automated data retrieval and forwarding to attending physician. Results. By the end of May 2016, 85 patients were included in the study with 39 of them already ended the course. A total of 11020 measurements of blood glucose, and 11747 meals recorded by patients into the application were analyzed. The average number of recorded days per patient was 49 (a minimum of 2 and a maximum of 128 days). The average glucose levels were 4.9±0.7 mmol/L at fasting state, 6.3±1.1 mmol/L-1 hours after breakfast, 6.2±0.8 mmol/L after lunch, and 6.2±0.9 mmol/L after dinner. In the analysis of food diaries the average daily energy intake was 1125±405 kcal and the daily consumptions of carbs, proteins and fats were 104±42, 66±25 and 60±22 g, respectively. These figures are well below the recommended dietary allowance for pregnant women, may be due to underreporting by patients. Conclusion. Although the study is being in progress, the general impact of app usage revealed a high convenience of this practice from the physician’s perspective. Current approach made it possible to preserve and organize the data, which might otherwise be lost or not collected. This data may be used in medical studies, carried out on patients with GDM. Keywords Gestational diabetes, monitoring, diary, mobile app, mHealth. Founding information The study was funded by Russian Science Foundation (project №15-14-30012).