Background: The purposes of this study, performed on a large sample of cancer patient-caregiver dyads, were: i) to simultaneously investigate, using an individualized quality of life (QoL) measure (Schedule for the Evaluation of Individual QoL, SEIQoL), the QoL domains freely expressed by cancer patients and their caregivers, and ii) to explore overlapping between the SEIQoL assessment and QoL assessment using traditional instruments.; Methods: The study employed a cross-sectional design including cancer patients who were going to receive chemotherapy treatment and their caregivers. Quality of life was assessed using condition-specific questionnaires (EORTC QLQ-C30 and CarGOQoL), generic health-related questionnaire (SF-36), and open individualized measure (SEIQoL).; Results: The final sample included 205 patient-caregiver dyads. From the SEIQoL, Family, Health, and Leisures were the most freely expressed QoL domains by patients and caregivers, but reported with different weights. Love life and financial issues were less spontaneously mentioned. The SEIQoL index was moderately correlated to the condition-specific QoL questionnaires (R lower than |0.40|) and to SF-36 (correlation coefficients: R ranging from 0.17 to 0.31).; Conclusion: Individualized QoL measures allow individuals to spontaneously express important, non-predefined domains. This study highlights the need to explore QoL using a combination of individualized questionnaires and standardized questionnaires, capturing complementary facets that patients consider important in their life.