The need to evaluate ÏUrban IIó socio-economic programmes financed by the European Union's Structural Funds has stressed the role of evaluation during the decision making process. The implementation of those Programmes has been a major factor behind the rapid growth in evaluation practice. Programmes co-financed by Structural Funds are extremely complex in construction and involve a large number of participants as well as numerous qualitative and quantitative factors. In this context, purely quantitative evaluation techniques are not able to provide the necessary decision making frameworks and tools to inform about the impact of interventions and the processes involved in their implementation. In addition, the complexity of these interventions is such that an evaluation consists not only of observing and analysing events, but it also requires careful structuring so that the effects of a programme can be prudently judged. In order to deal with what is a complex evaluation scenario, evaluators have to focus on the relevant factors, primarily those of the degree of complexity, and the timing of the evaluation, employing mixing and matching tools and techniques in a single evaluation method. The aim of the paper is to describe the role of evaluation in the decision making process and in the construction and implementation of Programmes; the analysis of the most used methodologies; the comparison of the best practices in the Italian financed Programmes and to understand how the evaluation could help the effectiveness and the efficiency of the investments in property markets and urban areas involved in the projects.