This study investigated the relationship between acute stress disorder (ASD) and posttraumatic stress disorder (PTSD) and comorbid anxiety, depressive, and substance use disorders over the first 12-month period following a cancer diagnosis. Individuals recently diagnosed with 1st onset head and neck or lung malignancy were assessed for ASD within the initial month following their diagnosis and reassessed for PTSD and other psychological disorders at both 6 months and 12 months following their cancer diagnosis. The incidence for PTSD at 12 months (14%) was lower than the incidence for other anxiety (20%) and depressive (20%) disorders. This study points to the need for the development of valid therapeutic interventions to assist this population in the 1st year following their diagnosis.