Recently the interest of aerospace and automotive industries toward the study of the vibrational response of orthotropic shell structures has grown rapidly. The low and high-frequency responses can be correctly simulated by the Finite Element Method (FEM) or the Statistical Energy Analysis (SEA) respectively. Over the last few years some Trefftz methods such as the Variational Theory of Complex Rays (VTCR) has been proposed to address the medium-frequency range. In this paper the extension of the VTCR to orthotropic shell structures has been developed. The theory has been generalized to orthotropic materials and a significant numerical example has been proposed to illustrate the effectiveness of the method.