The essence of modelling is to reflect the studied piece of reality in such a way that best describes the selected elements of the designed system. A model is used in design to optimize the structure and parameters of the constructed object and is a tool for assessing the quality of construction, eliminating weak links and ensuring adequate safety components. In view of the aim of modelling, it can be divided into functional modelling, showing the complexity of the object, and reliability modelling, specifying its states at variable threshold values. In design, modelling allows for significant savings in resources that would otherwise be spent because of problems appearing at the prototype stage, but also during production or in the course of using the product. In the practice of ergonomic design many problems could be avoided if early enough in the design process the values of parameters and their relations would be taken into account through modelling. On the other hand, the modelling process can be costly and time-consuming to carry out, and against the currently pervasive lean production it is a highly undesirable factor. Therefore, the modelling process should be supported with the use of appropriate cognitive techniques namely ethnography design, which would determine inadequacies of existing models as well as indicate the equivalent conditions for modelling. The justification of the use of this technique results both from the possibility of providing additional information, as well as the opportunity to "test" the phenomena affecting the design process. Ergonomic modelling tests developed solutions towards their adaptation to users' anthropometric, biomechanical and psychomotor characteristics, as well as behaviour patterns. However, knowledge of the latter and achieving a sufficient ergonomic and functional quality of proposed solutions often requires the use of the ethnography design approach. The aim of this article is to test the practical application of ethnography design methodology in product design and to analyse the benefits of its use. The analysis is based on effects of its application with the support of product design from various industries, along with a discussion of the method's limitations. Among benefits of ethnography design, the greatest proved to be providing knowledge of nonspecific user behaviour previously unknown to designers, which when rendered by models allowed to develop innovative solutions.