The SO molecule has been studied by photoelectron spectroscopy using vacuum ultraviolet radiation from a synchrotron as the photon source. Both constant ionic state (CIS) and photoelectron spectra have been recorded. Resonances which appear in the CIS spectra recorded for selected vibrational levels of SO+ X (2) Pi in the photon energy region hv = 11.5-15.0 eV have been assigned to excitations to Rydberg states which converge to the SO+ a (4) Pi and A (2) Pi states and autoionize to SO+ X (2) Pi. Also, resonances which appear in the CIS spectra recorded in the photon energy region 15.0-16.4 eV for selected vibrational levels of SO+ b (4) Sigma(-) have been assigned to excitations to Rydberg states which converge to SO+ B (2) Sigma(-) and autoionize to SO+ b (4) Sigma(-). Photoelectron spectra recorded at selected resonant photon wavelengths show that autoionization can dramatically alter the intensities of the vibrational components in a photoelectron band and may allow extra vibrational structure to be observed. The additional information obtained from using this method to study short-lived molecules is discussed.