Introduction/background: Non-profit organisations are geared towards achieving public goals. They are very capable of formulating missions, the formal manifestation of which is a mission statement. A mission statement can be viewed as an element of the expression of organizational identity. An analysis of mission statements can be one way to determine a non-profit organization’s raison d'être, priorities, course of action, etc. Their axiological system may also be described on this basis. Aim of the paper: The aim of the article was to answer the following research questions: What activities do non-profit organisations expose in their mission statements? What beneficiaries do non-profit organisations indicate in their mission statements? What values do non-profit organisations profess in their mission statements, and what values are declared by their leaders? What are the motives for non-profit organisations to formulate mission statements? Materials and methods: In the study, the mission statements of 320 Polish non-profit organisations were examined. A certain limitation of the research was the purposeful selection of the sample, resulting from the fact that a significant part of Polish NPOs have no formulated missions. The text content of these mission statements was analysed using IRAMUTEQ software. To obtain additional data, as well as to enable its triangulation, supplementary questionnaire surveys were sent out to the leaders of these 320 non-profit entities. Results and conclusions: The studies allowed the authors to fill in the research gap concerning the mission statements of Polish NPOs, the goals of their formulation, as well as the values they contain. It was found that the formulation of mission statements served non-profit organisations mainly to communicate with the society. In fewer cases, it was part of the strategic management process. In the disclosed mission statements, non-profit organisations communicated their goals, forms of activity, clients and core values. Research also showed that analyses of the content of mission statements can be an important source of knowledge about non-profit organisations, including their axiological system. Literature emphasises that these organisations are value-driven, but examples of the values and their prevalence are rarely explored. To identify values professed by non-profit entities, Whitman’s (2009) catalogue was used, supplemented – as a result of the conducted research – with additional social values. The presence of economic values in mission statements and leaders' declarations was also tested, having been analysed in the context of economisation and professionalisation in the third sector. It was demonstrated that economic values are important for non-profit organisations, although they are not as strongly prioritised as social values.