BACKGROUND: We set out to explore whether patients with life-threatening illnesses and their informal carers consider they experience significant spiritual needs, in the context of their overall needs, how spiritual concerns might vary by illness group and over the course of the illness, and how patients and their carers think they might be supported in addressing spiritual issues. METHODS: Three-monthly qualitative interviews for up to one year with 20 patients with inoperable lung cancer and 20 patients with end-stage heart failure and their informal carers. RESULTS: We conducted 149 in-depth interviews. Spiritual concerns were important for many patients in both groups, both early and later in the illness progression. Whether or not patients and carers held religious beliefs, they expressed needs for love, meaning, purpose and sometimes transcendence. The different experiences of lung cancer and heart failure raised contrasting patterns of spiritual issues and needs. Carers voiced their own spiritual needs. Patients and carers were generally reluctant to raise spiritual issues, but many, in the context of a developing relationship with the researcher, were able to talk about such needs. CONCLUSIONS: Spiritual issues were significant for many patients in their last year of life and their carers. Many health professionals lack the necessary time and skills to uncover and address such issues. Creating the opportunity for patients and carers to discuss spiritual issues, if they wish, requires highly developed communication skills and adequate time.