The three-dimensional power Korteweg-de Vries equation [ u t + u n u x + u x x x ] x + u y y + u z z = 0 , is considered. Solitary wave solutions for any positive integer n and cnoidal wave solutions for n = 1 and n = 2 are obtained. The cnoidal wave solutions are shown to be represented as infinite sums of solitons by using Fourier series expansions and Poisson's summation formula.