The issues of risk management in small and medium-sized enterprises (SMEs) have been analysed and discussed for a long time. Nevertheless, it is still necessary to concentrate on this field, especially in the Slovak Republic. SMEs are very sensitive to changes in the business environment which are always reflected in the quantitative characteristics of this sector in a certain time interval. According to various global surveys and studies, risk management represents a significant contribution to the increasing competitiveness of enterprises in changes of the business environment. The aim of this paper is to statistically assess the dependence of perceived key business risks of SMEs on their size in Slovakia based on own empirical research carried out in 2017. The contribution also includes an assessment of key risk sources and an evaluation of the survey results compared to the results of surveys taken last year. Based on the results, market, financial, economic and personnel risks comprise the four most important risks that negatively affect the business environment of SMEs. Dependence perceived by the SME entrepreneurs was found among market factors, personnel risks, and business size. No dependence was found among the financial, economic and business risks. The overall results of the empirical research point to the need and importance of addressing the assessment of key risks and their resources in SMEs in Slovakia. The goal of the paper is to highlight through a relevant study the need to apply risk management in the SMEs and to bring the results of the research in Slovakia closer to world trends.