In this contribution a simple and effective technique for the numerical calculation of the Green's functions in cylindrical shaped enclosures is developed. The technique is based on the numerical imposition of the boundary conditions for the fields at the cylindrical walls, using the theory of images. Numerical results for the Green's functions inside a cylindrical cavity are presented, including convergence test of the algorithm. Results show that numerical convergence is attained fast, therefore demonstrating the usefulness of the developed algorithm.