Polyurethane (PU) foams are highly versatile cellular polymers, used in wide range of industrial applications, such as mattresses and pillows, upholstered furnitures, car seats and packaging. Most common PUs are formed by reaction of a di- or polyisocyanate with a polyol. Depending on the chemicals and formulations used for the synthesis (nature and stoichiometric ratio of polyol and isocyanate, water content, surfactant amount, etc.), PUs with different density, morphology and physical properties can be obtained, in order to properly fit the desired application. In this work three different commercial flexible PU foams, used for mattress fabrication, were analyzed in order to investigate the influence of their composition on apparent density, cellular structure, water permeability, resilience and compression mechanical properties. In particular, with the aim to improve the understanding of factors affecting the foam comfort in static conditions, stress–strain measurements in 25% and 65% compression and hysteresis tests have been carried out that allowed to highlight the differences in terms of recovery rate, sag factor and hysteresis loss of the analyzed foams.