Purpose CyberKnife stereotactic radiotherapy (CSR) may require fiducial markers (FM) implantation to treat early stage malignant lung neoplasm. Percutaneous insertion of FM may be hazardous in some patients due to comorbidities and technical limitations. The goal of this study was to retrospectively evaluate the safety and efficacy of endovascular FM insertion for CSR treatment planning of lung neoplasms. Materials and Methods After institutional review board approval, we retrospectively reviewed the files of the 12 patients (7 males and 5 females) aged 62 to 83 years old who had endovascular insertion of FM (5 gold seeds in one patient and 45 0.018” embolization coils in 11 patients) via the pulmonary arteries from January 2010 to October 2013 as part of motion corrected CSR planning. The distance between each marker and the tumour was measured and the number of coils used for treatment planning and complications were recorded. Results Four (10 patients) or 5 (2 patients) endovascular FM were inserted. All patients were non surgical candidates because of severe COPD (7 patients) or other associated comorbidities (5 patients). Transthoracic percutaneous FM insertion was considered too dangerous in all patients. CSR planning and treatment were done using endovascular FM in 10 patients while 2 patients did not receive radiation treatment, one because of a concurrent diagnosis of diffuse large B cell lymphoma and another because the lung nodule decreased in size on follow-up exams. CSR planning was possible in all 10 remaining patients. Out of 50 FM, 8 were excluded in the 2 patients who did not have radiation treatment, 31/42 (74%) were deemed adequate by the radio-oncologist and 27/42 (64%) were used for the CSR planning. Fifteen FM were excluded: 1 gold seed because of migration, 4 coils because of distance from the tumour, 6 coils because they didn’t move with the tumour during treatment planning and 4 coils for unknown reasons. No complication related to the endovascular procedures was reported. Conclusion Endovascular insertion of FM is a safe and efficient alternative to percutaneous implantation in patients with early lung neoplasm that are candidates to CSR.