Our aim was to evaluate prospectively the effects of decompression as the primary treatment of large mandibular cysts, irrespective of their histological type. Twenty patients with large mandibular cysts completed treatment successfully. After a mean duration of decompression of 446 days, cysts had shrunk by a mean of 81%. Mean follow-up was 527 days after removal of the decompression stent and removal of the cyst. There were no recurrences. The advantages of this approach are simplicity, immediate gathering of information on the type of cyst with simultaneous start of treatment, low morbidity and low incidence of complications during treatment. Despite the length of the treatment, we recommend the use of decompression stents in the treatment of large mandibular cysts.