To probe magnetic ordering in single crystals of La1-x MnO3 (x = 0.01, 0.05, 0.13) and in ceramics of LaMn1-yO3 (y = 0, 0.02, 0.06), the X-band electron magnetic resonance measurements were carried out in the temperature range 5 K les T les 600 K. The temperature dependences of doubly integrated intensity of electron paramagnetic resonance signal and its linewidth were fitted with known theoretical models modified for taking into account the different mechanisms of spin relaxation. The experimental data and their fits evidence that Mn- and La-site vacancies dope the holes in parent LaMnO3, which induces ferromagnetic double exchange interaction. However, strong structural and chemical disorder of La1-xMnO3 crystals makes the ferromagnetic ground state eventually impossible even at x = 0.13. In a contrast, better structural/chemical homogeneity together with a stronger impact of Mn-site vacancies on mixed manganese valence and double exchange are characteristic for LaMn1-yO3 ceramics. As a result, the LaMn0.94O3 compound appears to be ferromagnetic-like ordered and demonstrates band-like propagation of doped carriers.