The electronic excited states of p-benzoquinone have been studied using multiconfigurational second-order perturbation theory (CASPT2) and extended atomic natural orbital (ANO) basis sets. The calculation of the singlet-singlet and singlet-triplet transition energies comprises 19 valence singlet excited states, 4 valence triplet states, and the singlet 3s,3p, and 3d members of the Rydberg series converging to the first four ionization limits. The computed vertical excitation energies are found to be in agreement with the available experimental data. Conclusive assignments to both valence and Rydberg states have been performed. The main features of the electronic spectrum correspond to the pi pi* 1 (1)A(g) --> 1 B-1(1u) and pi pi* 1 (1)A(g) --> 3 B-1(1u) transitions, computed to be at 5.15 and 7.08 eV, respectively. Assignments of the observed low-energy Rydberg bands have been proposed: An n --> 3p transition for the sharp absorption located at ca. 7.4 eV and two n --> 3d and pi --> 3s transitions for the broad band observed at ca. 7.8 eV. The lowest triplet state is computed to be an n pi* B-3(1g) state, in agreement with the experimental evidence.