This longitudinal, qualitative, descriptive, and exploratory study aimed to identify and understand the food preferences and aversions arising from hematopoietic stem cell transplantation (HSCT), chemotherapy, and/or radiotherapy treatment. An open and individual interview was carried out with patients diagnosed with hematological diseases or cancer, submitted to HSCT, chemotherapy, and/or radiotherapy treatment. The participants answered the following questions: "Have you experienced any changes in taste since the beginning of radiotherapy/chemotherapy?"; "Have you experienced any strange taste in your mouth, aversion or preference for a certain food that did not exist before the beginning of radiotherapy/chemotherapy?" The software IRAMUTEQ (R Interface for Multidimensional Analysis of Texts and Questionnaires) version 0.7 alpha 2 was used for textual analysis, with similarity analysis and word cloud. One hundred and forty six patients were included in the study, 50% (n = 73) female and 73% (n = 50) elderly. The main words reported by the participants in regards to food aversions were "meat", "beef" and "chicken", which are related to dysphagia. Regarding food preferences, the most mentioned words were "fruits", "juices" and "soups", whose consumption was associated with an improvement in gastrointestinal symptoms, especially nausea. Adjustments in the diet plan based on this information can contribute to a better acceptance of the diet, and clinical and nutritional prognosis.