Access to finance represents one of the biggest obstacles that micro and small enterprises (MSEs) face, in the world as well as in the Republic of Croatia. Previous research confirmed that MSEs` growth and development are strongly related to available financial sources. Numerous studies that deal with this issue emphasize the importance of the factors influencing the availability of financial sources for MSEs for further research, as well as the relationship between sources of financing and MSEs performance. In this doctoral dissertation, the characteristics of entrepreneurs and enterprises, as well as the business obstacles were analyzed as factors influencing access to finance for MSEs. Furthermore, the relationship between used and realized sources of financing was examined with regard to the MSEs performance. Empirical research was conducted on a sample of 173 MSEs from the Dalmatia region. The analysis determined that factors influencing MSEs access to external sources of financing are: financial literacy and a higher level of education of entrepreneurs, a written business/strategic plan, a higher rate of company growth, higher rates of profitability and a lower level of perception of external business obstacles. Also, it is determined that there is a significant difference in the MSEs performance (measured by financial and non-financial performance measures) with regard to the used and realized sources of financing. The research confirmed that the majority of MSEs use and prefer internal sources of financing. However, income/employees growth is planned to the smallest extent by MSEs that did not apply external sources of financing. Furthermore, leasing and short-term business credits are the most common external source of financing for the majority of MSEs. The biggest obstacles for obtaining a loan were identified: the interest rate level, the amount of required collateral, high requirements regarding the credit rating and the length of the loan approval process. Besides that, as the most common reasons for loan rejection are failure to meet the required criteria and the complexity of the loan approval procedure. The largest share of entrepreneurs consider that they do not need special financing programs. In addition, the most common reasons for not applying for those programs refers to the length of the procedure for approving and obtaining funds as well as unfamiliarity with the programs. MSEs that did not obtain external sources of financing achieve lower performance indicators compared to MSEs that were successful in obtaining them. Therefore, in order for MSEs to be successful, they need to overcome credit constraints.The intention and research objectives as well as sources and data collection methods are described in the introduction. In line with the set research objectives, the structure of dissertation was developed, and is made of nine chapters: Introduction; Characteristics of micro, small and medium enterprises; Factors influencing the access to financial resources for MSEs; Financing micro and small enterprises; Business performance measures; Financial environment of MSEs in the Republic of Croatia; discussion and conclusion is followed by the results of the conducted empirical research.