OBJECTIVE: The aim of the present study was to evaluate the accuracy of an extraoral CBCT-planned 3D-printed surgical guide aimed to percutaneous injection of substances into the temporomandibular joint (TMJ) and the lateral pterygoid muscle (LPM). METHODS: Nine human cadaver heads were used. Pre-planning CBCT and facial scans were obtained and three percutaneous injection sites were planned: one for the lower compartment of the TMJ and two for the LPM. A digital surgical guide was then designed with small titanium sleeves and printed by a 3D printer. After the injections, new CBCT scans with the needles in place were obtained in order to assess the accuracy of the procedure in relation to the virtual planning. RESULTS: The mean values for angle deviation were very low (range 1.13o-4.08o), the same happening for the mean difference in the length reached (range 1.82-2.64 mm), as well as for the mean difference in the needle tip dislocation (range 0.94-2.03 mm). CONCLUSION: The guide seems to be a reliable tool for accurate percutaneous injection of drugs into the inferior compartment of the TMJ and the LPM. Further studies are necessary to test the efficacy and validate the method in an in vivo study.