Аннотация:We compare two different approaches to compute the effects of vacuum polarization associatedwith a massless scalar field near pointlike source with a zero-range potential in three spatial dimensions.The first one consists in the usage of delta-like sequence of regular potentials,regarding the limit as a model of pointlike interaction. We use the perturbation theory in the Fourier space. The second approach implies the self-adjoint extension technique. We compute the renormalized vacuum expectation value of the field square in a non-perturbative sense.