The goal of this paper is to present some of the work conducted in order to create a cash-flow DSS that aims to improve the financial decisions of Romanian small and medium enterprise managers. In order to create the desired DSS two major stages were followed: the construction of models for various financial decisions and the implementation of those models within the knowledge base of the DSS. The present paper covers the first stage while the second stage will be presented in the next article. For a better understanding, the paper is divided into three parts: theoretical considerations, practical application of theory and conclusions. The theoretical part builds up on basic definitions and previous decision theory research, and, taking into consideration different modeling methodologies, establishes the necessary steps and tools that will be used in the second part. The second part establishes the decisional situations that will be modeled, briefly describes each of them and shows the models devised according to particularities of small and medium enterprises. The goal of this part is to create a model (variables, relations between them, etc) that is suited for implementation in a cash-flow DSS. In the final part some conclusions are stated and the future research direction is established.