The integration of an MPD system during a new drilling floater design phase is today a common practice. While working on a brand new project, different MPD technologies could be evaluated choosing the one that suit best next well campaign properties of each drilling contractor. At the design phase, technically speaking, almost everything can be arranged and integrated. Now, given the high appeal that MPD systems are reaching today within Oil Companies, and considering the best possible delivery time for a new floater, are we sure we will be granted all this time to wait? The idea of limiting MPD chances to new builds seems not to be wise, thus, the profitability of retrofitting this new philosophy on an existing drilling rig should be properly evaluated. Developing this assessment, it is easy to notice how the implementation of an MPD set up on a conventional drilling plant impose the designer a different approach. Limitations in space on decks, integration between new and existing equipment and need for crew training are just some of the criticalities the drilling contractor will face choosing the best solution for them within the increasing number of potential providers. Let's say "constrains" will drive the choice. The two major technologies available in the MPD market - and relevant set up - have been analysed on a "retrofitting point of view", highlighting benefits and deficiencies of each in a critical tradeoff between drilling development and operative constrains.