Purpose: The aim of the article is to show the importance of reasoning (cognitive models) and experience of managers as a key success factor in implementation of management information systems (MIS). An important goal of the article is also to identify information needed and the importance of information and management decision support systems in healthcare which is one of the important sectors of the economy. Design/Methodology/Approach: The article is based on secondary and primary research. The literature in the area of decision support systems in management and factors that influence the success of implementing these systems were analysed. Quantitative and qualitative research was carried out on the information systems of health care facilities and information needs of decision makers. The conclusions of the research were based on the following research, in-depth group interviews (FGI), individual in-depth interviews (IDI) with directors of medical facilities (27), interviews with facility employees (PAPI), interviews with patients (PAPI), Delphi study using the CAWI technique. Findings: There is a great need to implement decision support systems due to the growing amount of information available to managers and the need to process it quickly. Practical Implications: The article presents a unique approach showing how the cognitive systems of managers and their way of reasoning influence the type and specifics of management decision support systems. Originality/value: The article presents a unique approach showing how the cognitive systems of managers and their way of reasoning influence the type and specificity of management decision support systems.