Objective: to analyze the contents and dimensions of social representations about chemotherapy by cancer patients in chemotherapy treatment. Method: qualitative study, based on the Theory of Social Representations. One hundred patients were interviewed with cancer undergoing chemotherapy treatment attended at a High Complexity Oncology Unit located in the north of the state of Paraná between August and December of 2016. To collect data, a socio-occupational and clinical characterization questionnaire was used, a form of free evocations and in-depth interviews. The analysis was performed with the softwares Microsoft Excel and Evocations. Results: the social representation of chemotherapy has in its central core the words healing, good and difficult, which are structured in order to justify the completion of chemotherapy - good treatment that leads to healing, although difficult. In addition, an attempt is made to define chemotherapy from its effectiveness, seeking, in healing, its conceptualization. The periphery presents elements related to the attitude, efficacy and side effects of chemotherapy, which reveal the concrete experience of daily life during treatment. Conclusion: the health team, especially the nursing team, should collaborate with the representational construction of patients with cancer in chemotherapy, offering information and rescuing knowledge gaps that allow their participation in the therapeutic process.