Exposure to cooking fumes may be responsible for respiratory health effects. However, the linkage between such exposures and these effects cannot be established without knowing the size distribution of the aerosols emitted from cooking activities. This study examined the size distribution of the aerosols generated by commercial cooking processes. It was found that the aerosol size distributions were lognormal. Several theoretical models can explain the lognormal characteristic of aerosols from cooking processes and the simplest one is a bounded multiplicative process that represents the growth (or shrinkage) of aerosols in a random manner. Our results showed that by defining the mode diameter (geometric mean diameter) and the dimensionless geometric standard deviation one could describe the size distribution of cooking fumes in general. This characterization model can be applied to cooking fumes from indoor as well as outdoor cooking processes. The results of our measurement also showed that the mode diameter of aerosols increased when cooking temperature increased. The normalized number concentration of sub-micrometer aerosols increased rapidly when cooking temperature increased especially in the size range between 0.1 and 1.0 μm, known as the accumulation mode.