A detailed description of the P band system of the NO molecule has been achieved by calculating electronic transition moments, Einstein coefficients, and radiative lifetimes. The known strong interaction of the B(2)Pi valence state with Rydberg states of (2)Pi symmetry is treated through a vibronic interaction matrix. This actually implies an extension of the molecular quantum defect orbital (MQDO) methodology in the study of vibronic levels of diatomic molecules. The MQDO approach has recently led to rather good results in the study of the 3ssigma(A(2)Sigma(+))-X(2)Pi (gamma band), 3psigma(D(2)Sigma(+))-X(2)Pi (epsilon band), and 3psigma(D(2)Sigma(+))-3ssigma(A(2)Sigma(+)) transitions.