A preliminary design of a polygeneration system (combined cooling-heating-power plant with a desalination unit), is proposed for a tourist resort located on the Spanish coast. The well-known trigeneration concept is enhanced to the included production of desalted water, considering for the purpose three different options: Reverse Osmosis (RODP), Multi-effect (MEDP) and a combination of RODP and MEDP units. The preliminary design is obtained with a model established as an optimization problem. The influence of the operation mode is also considered in the analysis. The results show that the integration of an internal combustion engine, a LiBr-H2O single effect absorption chiller and a MEDP desalination unit is the most suitable configuration. From an economical point of view, the optimal operation mode is achieved when the prime mover works at full load, but in this case, the lowest greenhouse gas (GHG) emission reduction and primary energy savings (PES) are obtained. The second profitable operation mode is the one following the thermal demand which achieves the highest GHG emission reduction and PES.