The method to deduce the atomic orbitals constituting a valence band from two-dimensional photoelectron angular distribution (PEAD) (called ODAD: orbital determination from angular distribution) is fully discussed. The two-dimensional PEAD pattern obtained by using linearly polarized light is characteristic of the initial atomic orbitals. If the initial electronic state is localized and a wide-angle two-dimensional PEAD pattern is observed, the component ratio of atomic orbitals can be deduced by fitting the observed PEAD with calculated patterns. When only a limited area is observed by the effect of band dispersion, we can change the polar angle θ p or the azimuthal angle φ p of the sample with respect to the incident photon so that we can get enough information. Even and odd symmetries are easily distinguished when we measure the φ p dependence of the photoelectron intensity. The θ p dependence at a special direction (θ k ,φ k )=(45,35) is proposed to distinguish all atomic orbitals.