When a small and medium-sized enterprise (SME) decides to invest in an innovative project, it becomes attached to a high level of uncertainty (Hall & Lerner, 2009) and it could meet some financial constraints (Kerr & Nanda, 2014). This work is trying to apprehend the specific financial problems which SMEs, working on innovative projects, might face in a context characterized by a lack of liquidity, and it aims to improve the understanding of previous theoretical and empirical studies that dealt with the subject of financing these innovative companies.Moreover, it appears that it is important to ask the following question: Are there specific financial constraints to innovative SMEs? In order to answer the preceding question, this paper presents firstly the concept of innovation within companies. Secondly, it describes the specificities bound to the diverse financing approaches: in terms of risk, uncertainty, asymmetric information and profitability of an innovative project, while developing a theoretical approach concerning the possible constraints of financing the innovative companies.