Studies on the effectiveness and efficiency of palliative care (PC) services that use a methodology similar to that used by studies in other medical specialties face serious limitations, since the goals of PC are substantially different. Qualitative research methods can make an important contribution to our understanding of the features of palliative care (PC) that are most relevant to patients and their relatives. The goal of this study was to understand the reasons behind the gratitude shown in letters from bereaved relatives sent to two PC units, one in Spain and one in Portugal. A thematic analysis of the content of the letters was independently carried out by three researchers, who later collaborated to write up the results. Relatives appeared grateful primarily for the humane attitude, professional treatment, and emotional support that their loved ones received from the PC team; they thanked the team for creating a special atmosphere and offering holistic care, and they talked about the contrast between PC and other forms of care. The unsolicited gratitude expressed in their letters constitutes a valid and particularly rich source of information about the contribution that a PC team can make.