This therapy process study investigates the use of guided affective imagery for tumor patients. The therapeutic access to tumor patients is generally described as complex and challenging because of a disturbed emotion regulation and a defensive focus on reality. After autologous blood stem cell transplantation, 29 patients were treated with psychotherapy, including two daydreaming imagery sessions. Three text-analytical measures--Affective Dictionary Ulm, Regressive Imagery Dictionary, and Computerized Referential Activity for verbatim session transcripts--as well as the Quality of Life Questionnaire and the Karnofsky Performance Status were administered. Results show that guided affective imagery was able to enhance the psychotherapeutic process in tumor patients by activating the primary process, decreasing anxiety, and increasing referential activity. The positive emotional shift during imagery was achieved by the patients irrespective of their oncological severity status. Study limitations and future directions for research are discussed.