To assess whether the optimal mean arterial blood pressure (MAP) target after out-of-hospital cardiac arrest (OHCA) is influenced by age and a history of arterial hypertension. Post-hoc analysis of data from the Blood Pressure and Oxygenation Targets in Post Resuscitation Care (BOX) trial. The trial included 789 comatose patients randomized to a MAP target of 63mmHg or 77mmHg. The primary outcome of this sub-study was one-year all-cause mortality. Cox proportional-hazards regression and restricted cubic splines were used to examine whether prevalent hypertension and age modified the effect of low versus high MAP target on all-cause mortality. Of the 789 patients randomized, 393 were assigned to a high MAP target, and 396 to a low MAP target. Groups were well balanced for mean age (high MAP target 63±13 years versus low 62±14 years) and hypertension (45% versus 47% respectively). At one year, the primary outcome occurred in 143 patients (36%) with high MAP target and 138 (35%) with low MAP target. The risk of the primary outcome increased linearly with increasing age (P<0.001). The effect of a high versus low MAP target on the primary outcome was modified by age when tested continuously, potentially favoring low MAP target in younger patients (P for interaction=0.03). Prevalent hypertension did not modify the effect of a high versus low MAP target on the primary outcome (P for interaction=0.67). Among patients resuscitated after OHCA, older patients and those with a history of hypertension did not benefit from a higher MAP target.