The 17,18O(p, n) 17,18F reactions were studied at Ep = 35 MeV. Neutron spectra were measured at laboratory angles between 0° and 140°. Results were compared with distorted-wave calculations using the shell-model wave functions. For the 17O(p, n) reaction, cross-section magnitudes as well as the angular-distribution shapes were well described by the calculation. On the other hand, normalization factors of 0.60 were required for the spin-flip excitations observed in the 18O(p, n) reaction leading to the ground (1 +), 1.700 MeV (1 +) and 2.100 MeV (2 -) states. Possible origins of such differences were discussed.