Irradiation of cadmium particles in aqueous solution by a pulsed Nd:YAG laser at 355 nm was found to cause size reduction of the particles. The temperature of the cadmium particles was calculated from the laser energy absorbed by the particles, and was found to increase as high as the boiling point of cadmium. The shape change and size reduction are considered to occur through melting and vaporization of the cadmium particles. The results are explained on the basis of the rate of energy deposition compared with electron-phonon and phonon-phonon relaxation processes. The electron dynamics was studied in copper metal nanoparticles using transient absorption spectroscopy after excitation with 532 nm ps laser pulses.