75As nuclear quadrupole resonance (NQR) spin–spin (T2) and spin–lattice (T1) relaxation time measurements have been performed in glasses of the Ge–As–Se system as a function of average coordination number r. The results for T2 indicate that in compositions with high r the inhomogeneities in the local structure increase and clustering effects lead to nanoscale phase separation. There is evidence of the indirect interaction of As atoms (J-coupling) in these compositions. The spin–lattice relaxation occurs through “spin diffusion” when inhomogeneities in the spin system environment lead to the distribution of relaxation rates. We suggest that T1 measurements can provide a probe of the network rigidity in some glasses.