BACKGROUND: A 3D printing custom-made mask model was tested in terms of feasibility and accuracy for frameless neuronavigation during retrosigmoid approach. METHODS: A virtual 3D model of a cadaveric injected head was obtained from a high-resolution Computed Tomography (CT) scan and 3D Printed (3DP). The course of the transverse and sigmoid sinus was marked. A transparent custommade 3DP mask model was created as a cast of 3D model. The area of the lateral sinuses was grooved to allow the surgeon to use the mask as a template to draw the course of the sinuses on the patient skull. A right retrosigmoid approach was performed on formalin-fixed injected cadaveric head. Inion and other conventional landmarks were used to mark the course of the sinuses. 3DP mask was used to re-mark the course of the sinuses. The mismatch between the landmarks-based and 3DP mask-based track was assumed as a measure of the accuracy of the 3DP mask model. RESULTS: 3DP mask model resulted precise, feasible, easy and fast to use. A perfect interlocking with the retrosigmoid area was noted. Mismatch between the landmarks-based and 3DP mask-based track was of 4 and 6 mm for transverse and sigmoid sinus, respectively. CONCLUSION: 3DP custom-made mask model is feasible, easily reproducible and reliable for the implementation of a frameless neuronavigation during retrosigmoid approach. Its accuracy is greater than that of the bone landmark neuronavigation. In selected cases, 3DP mask can be a valid option to image-guided optical or electromagnetic tracking systems.