BackgroundCharacteristics of the physician influence the essential decision-making in end-of-life care. However, the effect of special education in palliative medicine on different aspects of decision-making in end-of-life care remains unknown. The aim of this study was to explore the decision-making in end-of-life care among physicians with or without special competency in palliative medicine (cPM).MethodsA questionnaire including an advanced lung cancer patient-scenario with multiple decision options in end-of-life care situation was sent to 1327 Finnish physicians. Decisions to withdraw or withhold ten life-prolonging interventions were asked on a scale from 1 (definitely would not) to 5 (definitely would) – first, without additional information and then after the family’s request for aggressive treatment and the availability of an advance directive. Values from chronological original scenario, family’s appeal and advance directive were clustered by trajectory analysis.ResultsWe received 699 (53%) responses. The mean values of the ten answers in the original scenario were 4.1 in physicians with cPM, 3.4 in general practitioners, 3.4 in surgeons, 3.5 in internists and 3.8 in oncologists (p < 0.05 for physicians with cPM vs. oncologists and p < 0.001 for physicians with cPM vs. others). Younger age and not being an oncologist or not having cPM increased aggressive treatment decisions in multivariable logistic regression analysis. The less aggressive approach of physicians with cPM differed between therapies, being most striking concerning intravenous hydration, nasogastric tube and blood transfusions. The aggressive approach increased by the family’s request (p < 0.001) and decreased by an advance directive (p < 0.001) in all physicians, regardless of special education in palliative medicine.ConclusionPhysicians with special education in palliative medicine make less aggressive decisions in end-of-life care. The impact of specialty on decision-making varies among treatment options. Education in end-of-life care decision-making should be mandatory for young physicians and those in specialty training.Electronic supplementary materialThe online version of this article (10.1186/s12904-018-0349-6) contains supplementary material, which is available to authorized users.