This paper concerns the p-maxian problem on trees with an upper bound on the distance of new facilities. We first consider the case p = 2 and show that the optimal objective is obtained if the constraint holds with equality. By this result, we further explore the characteristic of the optimal solution, which helps to develop a linear time algorithm to solve the constrained 2-maxian problem. The result can be extended to the constrained p-maxian on trees based on the nestedness property. We also discuss the constrained p-maxian problem on trees in relation to the unconstrained p-maxian problem and the 1-maxian problem on the underlying tree.