abstract: This work is made in collaboration with A. M. Rucklidge (Leeds). Quasipatterns (two-dimensional patterns which are quasiperiodic in any spatial direction) remain one of the outstanding problems of pattern formation. As with problems involving quasiperiodicity, there is a small divisor problem. In this talk, we consider 8 -fold, 10-fold, 12-fold, and higher order quasipattern solutions of the Swift--Hohenberg equation. We prove that a formal solution, given by a divergent series, may be used to build a smooth quasiperiodic function which is an approximate solution of the pattern-forming PDE up to an exponentially small error. Considering now the hydrodynamic Rayleigh-Benard convection problem, we are able to prove the same type of result for a steady quasipattern convective regime.