  In this note we address the problem of solving for the positronium mass
spectrum. We use front-form dynamics together with the method of flow
equations. For a special choice of the similarity function, the calculations
can be simplified by analytically integrating over the azimuthal angle. One
obtains an effective Hamiltonian and we solve numerically for its spectrum.
Comparing our results with different approaches we find encouraging properties
concerning the cutoff dependence of the results.
