The development of minimally invasive surgical technologies in the treatment of chronic paraproctitis is a promising young trend in coloproctology. Increasingly, in clinical practice, coloproctologists use laser technologies in the outpatient treatment of extra- and transsphincteric pararectal fistulas, in particular, laser technology FiLaC (Fistula Laser Closure). OBJECTIVE Conducting a comparative retrospective and prospective cohort study of immediate and long-term results of treatment of complicated transsphincteric and extrasphincteric fistulas using the developed modified FiLaC technology with the «traditional» FiLaC technology, and standard excision of the fistulous tract with plasty of the internal fistula opening with a full-thickness flap of the rectal wall. METHODS The study included 270 patients with trans- and extrasphincter pararectal fistulas, which were divided into three groups. In group 1 (n=90) the traditional FiLaC technology was used for the treatment of fistulas, in group 2 (n=90) the modified FiLaC technology was used, providing for the opening of purulent streaks and laser coagulation (FiLaC) of the intrasphincter part of the fistula with a Biolitec laser, 12 W, 100 J/cm, in group 3 (n=90), excision of the fistula tract with plastic surgery of the internal fistula opening with a full-thickness flap of the rectal wall was used. RESULTS The results of treatment in patients of the three groups were monitored for 19-36 months. after surgery (median 31 months). The analysis of the results showed that in group 2 (modified FiLaC technology) healing of fistulas occurred faster (7.3±0.5 weeks versus 12.6±0.7 weeks) compared to group 3 (excision of the fistula with plasty of the internal fistula opening). The indicators of sphincterometry in the long-term period in patients of the 2nd group were restored in relation to the initial ones, and in the th group 3 they were reduced compared to the initial values. Postoperative complications were most common in patients of group 3 (32.2%), and least often in patients of group 2 - 8.9%. At the same time, late postoperative complications were most common (24.4%) in patients of group 1. None of the patients in group 2 had late postoperative complications, while 11.1% of postoperative complications were recorded in group 3. In patients who underwent excision of the AC (group 3), relapses were most common: early - 15.6%, late - in 21.1%. The least frequent relapses were observed in patients who underwent modified FiLaC technology (Group 2): 6.7% - early relapses and 11.1% - late relapses. CONCLUSIONS The use of the modified FiLaC technology in the treatment of trans- and extrasphincteric fistulas of the rectum made it possible to minimize postoperative complications, fully preserve the function of anal holding, and achieve healing of fistulas in 82.5% of cases with a median follow-up of 31 months.