The wavelet transform (WT) was applied to event-related potentials (ERPs) elicited in oddball paradigm to investigate the presence of several functional components occuring in the P300 latency range. Quadratic B-spline WT was used to decompose the single-sweep ERPs into four octaves. The analysis demonstrates that several delta, theta, and alpha frequency components in the P300 latency range differ in latency and amplitude between target and nontarget processing. These findings indicate that P300 is composed of multiple functional components and the WT is a powerful technique to help study them.