Abstract-The highly competitive global environment of the last few decades has urged companies to rely on Information Systems (IS) in order to improve customer service, reduce costs and increase productivity. In that direction, Enterprise Resource Planning (ERP) systems are being used as significant strategic tools that provide competitive advantages and lead to operational excellence. Despite that, ERP implementation projects are complicated, costly and include high failure risks. The present study aims (a) to develop and (b) empirically test a conceptual framework that investigates the factors affecting ERP system effective implementation in Small and Medium Enterprises (SMEs). The examination of the conceptual framework was made with the use of a newly-developed structured questionnaire that was distributed to a group of Greek SMEs. After the completion of the research period, 159 usable questionnaires were returned. The reliability and the validity of the questionnaires were thoroughly examined, while research hypotheses were tested using the "Structural Equation This work was not supported by any organization.According to Garg and Garg [8], this "enables the decisionmaking process to be timely, consistent and reliable across organizational units and geographical locations" (p. 424).ERP implementation has various benefits throughout the organisation: elimination of redundant information, drastic declines in inventory, reduction of production cost, better understanding of the changing customer needs, more efficient management of the extended network of suppliers and customers, increased productivity, improved response time, and decreased production cycle [5] However, ERP implementation requires considerable financial resources, while the whole implementation project is considered complex, lengthy, and quite challenging [9] [ 1 3 ] . A s a r e s u l t , t h e s u c c e s s r a t e o f s u c h p r o j e c t s i s considered to be quite disappointing [14] [15] [16]. More specifically, Samuel and Kumar [17], argue that the success rate is, only, around 50%, while approximately 90% of ERP implementation projects are late, or over budget. On the same vein, Umble and Umble [18] reported failure rates between 50% and 75%. Therefore, additional empirical studies are necessary in order to assist companies in increasing the success rates of ERP implementation projects.Under that context, the aim of the present study is twofold: (a) develop an original conceptual framework (research model) examining the impact of various research factors on ERP implementation success, (b) empirically test that framework, using data from Small and Medium Enterprises (SMEs) located in Greece (empirical research).(a) The development of the conceptual framework was based on two methodological steps: firstly, a review of the literature identified the factors that were used by previous studies as antecedents of ERP implementation success; secondly, a panel of experts was used in order to discuss these factors and provide a list of the most si...