The growing importance of radial stub as a circuital element request an improvement in its analysis. In this paper a theorical model based on a planar approach, has been improved with the introduction of the effect of the losses. The determination of the Q-factors of the different TMon modes sustained by the structure actually represents a very simple and effective, even though approximate, method to take into account the effect of various causes of losses. In this way a resulting lossy model is available with good performance in a wide frequency range.