The paramagnetic properties of unpaired electron are effectively exploited in electron paramagnetic resonance spectroscopy (EPR). We shall see how the local structural properties of amorphous silicon are analyzed by EPR. The EPR results obtained on a-Si samples produced by ion implantation and magnetron sputtering will be compared. Moreover, the results of EPR analysis will be compared with GIXRD on the same materials. Finally we shall illustrate the effects of impurities like hydrogen and germanium on structural properties of a-Si.