Surgical treatment of head and neck cancer, in certain cases, inflicts large tissue defects. Some of these defects are associated with devastating functional deficits and disfiguring deformities. In addition, radiation therapy, whenever necessary, often leads to wound breakdown, dehiscence and fistula formation, due to healing mechanism impairment. The advent, development, and nowadays routine use of microsurgical techniques has revolutionized the reconstructive approach in this patient population and changed the outcomes dramatically. Free flap use has both ensured the best possible function and aesthetics and become the "gold standard" in complex head and neck reconstruction. Defects of the head and neck can be anatomically grouped into the following categories: a. Skull base, b. Midface, c. Tongue, d. Oral cavity, e. Mandible and f. Hypopharynx, larynx and cervical esophagus. Certain reconstructive goals should be met for each of these categories. Objectives of this article are threefold. First, to report the reconstructive goals in patients with head and neck cancer, second, to outline the indications of free flap use for each category of head and neck defects due to cancer therapy, and third to review in detail the free flap reconstructive options with respect to functional and aesthetic restoration for each kind of defect, according to the recent international literature.