In the paper we consider higher-order partial differential equations from the class of linear dispersive equations. We investigate solutions to these equations subject to random initial conditions given by harmonizable ϕ-sub-Gaussian processes. The main results are the bounds for the distributions of the suprema for solutions. We present the examples of processes for which the assumptions of the general result are verified and bounds are written in the explicit form. The main result is also specified for the case of Gaussian initial condition.Keywords Higher-order dispersive equations, random initial conditions, harmonizable processes, sub-Gaussian processes, distribution of sumpremum of solution, entropy methods 2010 MSC 35G10, 35R60, 60G20, 60G60