We have studied 3s(n(-1) and pi(-1)) Rydberg states and D-0(n(-1)) and D-1(pi(-1)) cationic states of pyrazine [1,4-diazabenzene] by picosecond (2 + 1) resonance-enhanced multiphoton ionization (REMPI), (2 + 1) REMPI photoelectron imaging, He(I) ultraviolet photoelectron spectroscopy (UPS), and vacuum ultraviolet pulsed field ionization photoelectron spectroscopy (VUV-PFI-PE). The new He(I) photoelectron spectrum of pyrazine in a supersonic jet revealed a considerably finer vibrational structure than a previous photoelectron spectrum of pyrazine vapor. We performed Franck-Condon analysis on the observed photoelectron and REMPI spectra in combination with ab initio density functional theory and molecular orbital calculations to determine the equilibrium geometries in the D-0 and 3s(n(-1)) states. The equilibrium geometries were found to differ slightly between the D-0 and 3s states, indicating the influence of a Rydberg electron on the molecular structure. The locations of the D-1-D-0 and 3s(pi(-1))-3s(n(-1)) conical intersections were estimated. From the line width in the D-1 <-S-0 spectrum, we estimated the lifetime of D-1 to be 12 fs for pyrazine and 15 fs for fully deuterated pyrazine. A similar lifetime was estimated for the 3s(pi(-1)) state of pyrazine by REMPI spectroscopy. The vibrational feature of D-1 bserved in the VUV-PFI-PE measurement differed dramatically from that in the UPS spectrum, which suggests that the high-n Rydberg (ZEKE) states converging to the D-1 vibronic state are short-lived due to electronic autoionization to the D-0 continuum.