The article presents the results of testing of the developed online-training of cognitive functions of the brain, which was implemented on a separately created game platform using a set of specially developed games. The proposed results reveal the theoretical justification of the cognitive functions, which are selected for training: memory, thinking, attention, imagination, perception. The characteristics of each cognitive function to be stimulated in the conditions of online games are highlighted. We described the algorithm for games evaluating according to certain cognitive functions and their characteristics. An analysis of the effectiveness of evaluation is given. The results of completing by players of game sessions balanced on the chosen cognitive functions are described. A comparison of the effectiveness of stimulation of different cognitive functions depending on the motivation and choice of players is presented. The aim of the study was to evaluate the effectiveness of online games in activation and stimulation of the cognitive functions of the human psyche. The research methods were based on our own developed algorithm for training success estimation, analysis of the results of online games, methods of mathematical statistics. The results of the study are presented on the basis of approbation of the developed training, conducted during two years. The analysis of the implementation of the training revealed the dependence of the effectiveness of stimulation of cognitive functions on the motivation and choice of the player. It is shown that when training on a balanced set of games, where all cognitive functions are present in equal shares, the effectiveness of training is not uniform and not balanced. It is investigated that the effectiveness of training depends on the quality of the game's effect on cognitive function. In order to take into account this quality of influence, all games were divided into two classes: actively shaping and passively stimulating. The distribution of games by classes was experimentally confirmed. A generalized analysis of the game sessions of all players for six months revealed cognitive functions which for the most players were better developed and more stimulated.