In recent years mission modularity has attracted the interest of European navies. Mission modularity allows increased flexibility in the use of naval assets and there is also clear potential  for life cycle cost savings due to economies of scale and reduced maintenance and upgrade costs. There is little hard data on the cost impact of mission modularity and on the prerequisites for achieving possible cost benefits, therefore Fincantieri and CETENA have been involved in a research  study, commissioned by EDA (European Defence Agency), in cooperation with Navantia (Spain) and Damen (Netherlands) shipyards, in order to investigate about life cycle cost of a modular naval fleet of frigates. The study has been divided in two parts: the first one consisting into the identification of the main characteristics of both frigate typologies (modular and “classical”) to be compared and the second one dealing with the assessment of a software tool able to identify the sources of the cost differences, evaluate their importance and recommend how mission modularity should be implemented to achieve maximum cost reduction with minimal compromising impact on capability. In this paper, the main aspects of the preliminary design of the modular frigate, adopted as reference for the life cycle cost evaluation, is described, together with a description of the software tool  that has been implemented.