In a recent prospective study,9 53% of hemangiomas had only a superficial component (Anita N. Haggstrom, MD, e-mail communication, November 2007), yet in our study all were either deep or both superficial and deep. Previous studies2,4,5 have suggested that deep hemangiomas may have a longer proliferative phase. In our cases, the component subjectively assessed to have prolonged growth was typically the deep component (Table and Figures 1-3). Our series also had an overrepresentation of hemangiomas involving the parotid gland (39%). Some authors10- 12 have asserted that parotid hemangiomas involute more slowly and are more resistant to systemic therapy than other hemangiomas. The findings in our cases support the concept of true differences in behavior in deep hemangiomas, including those with parotid involvement, rather than simply being an observational bias, and raise the question of whether the milieu in deeper sites is more permissive for growth than in more superficial sites. Parotid glands may have a higher-than-normal rate of blood flow,11 and Blei and Rutkowski13 noted high blood flow in hemangiomas at certain sites, particularly the parotid gland, but also the upper extremity, upper lip, and scalp, and suggested that they are “transiently arterialized,” causing slower involution than at other anatomic sites.