The paper presents a decision model and a tool that helps to find an information systems development methodology (ISDM) for a computer-based business information system (IS) that is suitable to a certain IS development project or an organisation dealing with IS development. The intention of the model is not only to suggest a certain ISDM, but also to propose the properties an ISDM should have to suite the project or the organisation. It is designed in a way that facilitates experimentation with different project, organisation and ISDM properties. Based on the model we created a tool that has been applied on several cases in which we validated the correctness of its recommendations and established that it can have a significant positive contribution in the process of ISDM selection and in the process of improvement of existing ISDM.