Hopefulness is believed to be a significant element in the human response to illness, but its clinical impact has not been documented due to conceptual and operational difficulties. This article generates a definition of hopefulness from well and ill adolescents. The study's conceptual orientation included the beliefs that hope is a contributing factor in health maintenance and is especially vital for individuals experiencing life-threatening illness. Grounded theory methodology was used. Interviews, observations and health records were data sources. Data were analyzed during the cross-comparative method. A panel approach was used to assess the reliability and validity of the induced categories. Theoretical saturation on a definition was achieved. Adolescents with cancer had a dimension in the definition not found in the other two groups. The added dimension had a focus on "others" in contrast to only "self."