Objectives: Research evidence about caregiver burden caused by patients with advanced cancer is scant. The purpose of this study was to identify which tasks were perceived as most time consuming and difficult of the Primary Caregivers (PC). Methods: The sample consisted of 100 Greek patients undergoing palliative radiotherapy and their PCs. They both provided their demographics, while patients completed MD Anderson Symptom Inventory (MDASI). PCs completed Oberst Caregiving Burden Scale (OCBS), consisted by two subscales (15 time and 15 difficulty items) measured in a 5- point Likert scale. Results: The majority of patients were male (63%) with a mean age 63.9 years and 5-10.000 € yearly income. Most of PCs were female (76%) and married (87%), with a mean age 52.9 years. The tasks perceived as most timeconsuming and difficult by PCs were providing transportation (mean 3.56) and emotional support (mean 3.53). Multiple linear regression analysis revealed that patient’s MDASI-symptom severity (p=0.046) accounted for 13% of burden variance of OCBS-Time. Patients’ MDASIinterference of symptoms with daily activities (p=0.084) and income (p=0.002) accounted for 22% of burden variance of OCBS-Difficulty. PCs with more total score of MDASI-symptoms interference and with lower income reported more total score of burden than those with less total score of MDASI-symptoms interference and those with higher income. PCs age (p=0.043) and marital status (p=0.041) accounted for 16% of burden variance by OCBS-Time. Aged and married PCs reported less total score of burden than younger and unmarried. PCs gender (p=0.016) and marital status (p=0.013) accounted for 10% of burden variance of OCBS-Difficulty. Conclusions: Despite study limitations, the results of this first Greek study assessing caregivers’ burden of advanced cancer patients, highlight that caring process can be demanding for families and that nurses have to identify ways to strengthen their ability in providing effective ways to support PCs.