Dielectric materials are used in many application areas. This paper introduces the application of a 3D capacitance CT for non-destructive evaluation of dielectric materials. The volumetric image of dielectric permittivity of the object is generated using the capacitance measurement data using an inverse finite element technique. The dielectric material inspection results in this work are presented by identifying present of air volumes (defects) inside a dielectric object. A sensor array has been designed and fabricated for the non-destructive testing application of capacitance CT. The paper presents both synthetic and experimental results.