  The particle discovered in the Higgs boson searches at the LHC with a mass of
about 125 GeV can be identified with one of the neutral Higgs bosons of the
Next-to-Minimal Supersymmetric Standard Model (NMSSM). We calculate predictions
for the Higgs-boson masses in the NMSSM using the Feynman-diagrammatic
approach. The predictions are based on the full NMSSM one-loop corrections
supplemented with the dominant and sub-dominant two-loop corrections within the
Minimal Supersymmetric Standard Model (MSSM). These include contributions at
$\mathcal{O}{\left(\alpha_t \alpha_s, \alpha_b \alpha_s,
\alpha_t^2,\alpha_t\alpha_b\right)}$, as well as a resummation of leading and
subleading logarithms from the top/scalar top sector. Taking these corrections
into account in the prediction for the mass of the Higgs boson in the NMSSM
that is identified with the observed signal is crucial in order to reach a
precision at a similar level as in the MSSM. The quality of the approximation
made at the two-loop level is analysed on the basis of the full one-loop
result, with a particular focus on the prediction for the Standard Model-like
Higgs boson that is associated with the observed signal. The obtained results
will be used as a basis for the extension of the code FeynHiggs to the NMSSM.
