Approximation of the Pareto Frontier Tomi Haanpää Most of the current Pareto frontier approximation models are for convex multiobjective optimization problems. In the convex case, one can construct very accurate approximation of the frontier, but the situation is totally different, if the problem is nonconvex. In a nonconvex case, one can have extremely badly behaving Pareto frontiers. Therefore the approximation model fitting process is not an easy task to do. One solution for the nonconvex case is an approximation of the image of the objective function and a classifier based approximation of the frontier by using the approximation of the image is illustrated.