Purpose Free flaps have become the standard option in reconstructive surgery of the head and neck. Even though many authors have outlined the reliability of free transplants, there is an ongoing discussion about treatment options for patients bearing particular risks as previous irradiation treatment. In this analysis, we aim to address these patients with particular risk profiles by comparing different flap entity outcome parameters. Methods We retrospectively analyzed a cohort of 494 patients who underwent flap surgery between 2009 and 2018 in our department. Focusing on free microvascular transplants, we additionally analyzed the pectoralis major myocutaneous flap as the most frequently used vascular pedicled flap. Data analysis was performed by uni-and multivariate statistics. Results Overall flap success rate was 90%, with the radial forearm flap occurring to be most reliable (93%) in head and neck reconstruction. Previous radiation therapy (RT) and intraoperative revision of vascular anastomosis during primary surgery significantly resulted in impaired transplant outcome with a success rate of 91.8% (no RT) vs. 83.7% (RT), respectively. There was a negative linear correlation between incision to suture time and number of flaps per year (R 2 = 0.67). Conclusions Preoperative radiation therapy and intraoperative revision of anastomosis significantly impair outcome of microvascular flaps in the head and neck and oral cavity, whereas patient's age is not a predictor of flap failure. Increasing case number and experience reduces time of flap surgery as well as rate of complications and flap failure.