The purpose of this prospective, longitudinal study was to determine if patients with lung cancer who are 65 years of age or older experience problems differently than do patients younger than age 65 during and following radiation treatment. The moderator and outcome variables selected for study were recognized attendant problems that may develop during lung cancer treatment and that may influence the treatment regimen and response. No statistically significant differences were found between patients age 65 or older and those younger than age 65 on caloric intake, adequacy of energy intake, total radiation dose, concurrent illnesses, and social support at any of four data-collection periods. Similarly, there were no significant differences on weight, body mass index, and multidimensional functional status. The relationship between the social support subscales and functional status measures for the 65-or-older group suggested that those subjects with lower social support perceived themselves to have better functional status. There was no relationship between social support and two functional status measures for the under-65 group. The significant relationships between social support and the overall health rating were in opposite directions for the two age groups. The results suggest that chronologic age alone may not be a sufficient criterion to determine therapeutic regimen or to suggest that unique problems may result.