In this study, the mechanical properties of submicrocellular or nanocellular thermoplastic polyurethane (TPU) nanocomposite foams were investigated via batch foaming using CO2 as the blowing agent. Cloisite 30B nanoclay (clay 30B) was the nucleation agent. Adding clay 30B and foaming at 60 degrees C resulted, in a nanocellular foam. A cell size of 450 nm and a cell density of 10(11) cells/cm(3) were obtained. The relative density of the foam was within the range 0.9-0.95. The modulus of the foamed samples was found to be proportional to their relative density regardless of their structure (microcellular/submicrocellular). The results indicated that the modulus of the foamed samples with a cell size larger than 400 nm decreased with foam density. However, to our surprise, although adding only 1 wt % of nanoclay reduced the foam density, an increase in the modulus was observed. In addition, the cells became small and uniform.