OBJECTIVE: To compare the difference in the clinical picture and outcomes between diabetic and nondiabetic patients with deep neck infections. STUDY DESIGN AND SETTING: We retrospectively reviewed the records of patients who were diagnosed with deep neck infections and who received treatment at the Department of Otolaryngology of National Taiwan University Hospital between 1997 and 2002. One hundred eighty-five patients were included in our study. Fifty-six patients with diabetes mellitus were enrolled for further analysis (diabetic group) and compared with the other 129 patients without diabetes mellitus (nondiabetic group) in demography, etiology, bacteriology, treatment, duration of hospital stay, complications, and outcome. RESULTS: The parapharyngeal space was the space most commonly involved in both the diabetic (33.9%) and nondiabetic groups (40.3%). Odontogenic infections and upper airway infections were the 2 leading causes of deep neck infection in diabetic and nondiabetic groups. Streptococcus viridans is the most commonly isolated organism in the nondiabetic group (43.7%). However, the most common organism in the diabetic group was Klebsiella pneumoniae (56.1%). There were 89.3% of diabetic patients, versus 71.3% of nondiabetic patients, with abscess formation ( P = 0.0136). Surgical drainage was performed more frequently in the diabetic group than in the nondiabetic group (86.0% versus 65.2%, P = 0.0142). In comparison with the nondiabetic group, the diabetic group tended to have older mean age (57.2 y versus 46.2 y, P = 0.0007), longer duration of hospital stay (19.7 days versus 10.2 days, P < 0.0001), more frequent complications (33.9% versus 8.5%, P < 0.0001), and more frequent tracheostomy or intubation (19.6% versus 6.2%, P = 0.0123). CONCLUSIONS: Patients with diabetes mellitus are susceptible to deep neck infection. We should pay more attention when dealing with deep neck infections in patients with diabetes mellitus because those patients tend to have complications more frequently and a longer duration of hospital stay. Empirical antibiotics should cover K. pneumoniae in patients with deep neck infection who have diabetes mellitus.