This paper examines the effect of processing temperature on polystyrene (PS)/CO2 and polycarbonate (PC)/ CO2 polymeric foaming systems. Using in situ visualization data from batch foaming experiments, plastic foam characteristics including cell density and average cell size at different processing temperatures were analyzed. These results were compared with those generated by computer simulation, and satisfactory agreements between the two were observed. It was found that the maximum cell densities in the PS/CO2 foaming system were higher at lower processing temperatures. For processing temperatures above the melting temperature of PC, a similar, but less significant, relationship between the maximum cell densities and temperature was observed for the PC/CO2 system.