Based on the 2005 and 2008 Chinese Longitudinal Healthy Longevity Survey, this study examined the prevalence of undermet needs for assistance in personal activities of daily living (ADL) and its associated risk factors among the oldest old aged 80+. Multilevel multinomial logistic modeling was used to analyze the risk factors and changes of undermet needs over time. The results show that the prevalence of slightly undermet needs decreased in urban China from 2005 to 2008. However, the prevalence of undermet needs remained high; 50% or more for both rural and urban residents. Compared to 2005, the likelihood of having slightly undermet needs in 2008 significantly decreased by 28% among rural residents and 22% among urban residents. The common risk factors of undermet needs among rural and urban residents included financial dependence, living alone, having unwilling caregivers, more ADL disabilities, and having poor self-rated health.