The deployment of Hybrid Offshore Wind and Wave Energy Systems (HOWiWaES) towards the simultaneous exploitation of the corresponding offshore renewable energy sources, may efficiently address the common challenge of the offshore wind and the wave energy sector to reduce their costs, with multiple additional benefits. A prerequisite at an early stage of the realization of a HOWiWaES project is the determination of marine areas suitable for the deployment of HOWiWaES. In the present paper, a methodological framework for identifying the most appropriate marine areas in Greece towards the deployment/siting of HOWiWaES is developed and presented. The framework is based on the combined use of multi-criteria decision making methods and Geographical Information Systems (GIS). At the first stage of the analysis, the unsuitable for the deployment of HOWiWaES marine areas are identified through the development of a GIS database that produces thematic maps representing exclusion criteria related to utilization restrictions as well as to economic, technical and social constraints. Then, at the second stage of the analysis, eligible marine areas not satisfying exclusion criteria are evaluated and ranked using the Analytical Hierarchy Process (AHP), based on evaluation criteria related to economic, technical and socio-political factors. The AHP's implementation is supported by the developed GIS database, eliminating significantly the subjectivity in judgments. The results of the paper illustrate the potential for deploying HOWiWaES in Greece, especially in the offshore areas of Crete and in a lengthwise zone extended from North-central to central Aegean.