To examine the impact of clinical predictors (pretreatment variables) and other influences (treatment and posttreatment variables) on long-term quality of life (QOL) in patients treated for squamous cell carcinoma of the upper aerodigestive tract. We hypothesized that baseline QOL and comorbidity would be predictors of QOL 1 year after treatment. Retrospective cohort study. Academic Medical Center in Seattle, Washington. Patients (N = 173) with baseline (pretreatment) and 1-year posttreatment QOL data. Head and neck-specific QOL scores at 1 year after treatment (as measured by the University of Washington Quality of Life [UW-QOL] scale). We identified strong relationships between 1-year UW-QOL scores and baseline UW-QOL scores (correlation coefficient [Pearson r] = 0.58; P < .001) and pretreatment comorbidity (as measured by the Adult Comorbidity Evaluation scale) (Spearman rho = 0.23; P < .001). T stage and N stage were also predictive. Although not a predictive variable, the presence of a gastrostomy tube at 1 year also strongly influenced 1-year UW-QOL scores. Patients with gastrostomy tubes had UW-QOL scores 11.5 points worse than those without (P < .001), when a 7-point difference is considered clinically significant. In predictive multivariate regression models, pretreatment QOL scores, comorbidity, and T stage had the strongest prognostic impact on 1-year UW-QOL scores. In bivariate analyses, the presence of a gastrostomy tube worsens UW-QOL scores at 1 year and requires further investigation. When considering predictive variables only, baseline QOL and comorbidity appear to have strong influences on posttreatment QOL and have greater impact than treatment modality. Greater attention to these baseline predictors should be given when counseling patients about long-term function after treatment.