A key focus of competition in the banking sector has become mobile banking, and in particular the functionality of the mobile applications offered, which are designed to provide customers with the convenience of using the full financial offer. In mobile banking, the customer is the party initiating the relationship, and the bank's role is reduced to providing a wide range of services and products, as well as ensuring maximum convenience and security of transactions. The remote model of relations with the bank places higher demands on the customer in terms of the level of necessary knowledge of the principles of mobile distribution channels and the conditions for the provision of banking services. In this context, aspects related to trust, commitment and customer satisfaction in the relationship with the bank become important. The purpose of this article is to assess the impact of the functionality of banking mobile applications on customer relationships with the bank. With regard to the objective, a hypothesis was formulated, which is: "The formation of lasting relationships between customers and their banks is determined by the functionality of the available mobile application." A systematic review of the literature on the subject was used as a research method, and the results of a self-reported survey conducted on a group of 450 active mobile banking customers were analyzed. The main conclusion of the own survey is that more than 90% of the respondents positively evaluated the used banking mobile application through the prism of the proposed dimensions of its functionality.