Nb thin films containing a regular square array of antidots with 17 nm diameter and 50 nm spacing have been fabricated using a relatively simple lithographic process. The critical current density jc(H) curves, obtained here by electric transport measurements, exhibit commensurability effects with pronounced maxima just above the expected μ0H1 = 0.830 T and μ0H1/2 = 0.415 T matching fields, down to temperatures as low as 2.3 K. The behavior of jc(H) as well as the position of the maxima are consistent with the ones calculated in the framework of the time dependent Ginzburg–Landau model.