Vertical excitation energies for the eight singlet-excited electronic states 1(1)E (2e --> 3s), 2(1)E (2e --> 3p(al)), 3(1)E (2e --> 3p(e)) 2(1)A(1) (2e --> 3P(e)) 1(1)A(2) (2e --> 3p(e)), 3(1)A(1) (2p(a1) --> 3s), 4(1)A(1) (2p(al) --> 3p(a1)), and 4(1)E (2P(a1) --> 3p(e)) of CH3F were investigated using the SA-MCSCF, MR-CISD, and MRCISD+Q approaches. Our results mostly confirm the experimental assignments but suggest some modifications for the main contribution to the maximum observed in the range from 12.5-14 eV. The dissociation channels for the production of fluorine atoms have been characterized. Potential energy curves for the dissociation of the CF bond under C-3v symmetry restrictions were computed for all states mentioned above leading to the ground-state dissociation channel CH3((X) over tilde (2)A(2)") + F((2)p), the excited-state channels CH3(3s (2)A(1)') + F(P-2) and CH3(3p (2)A(2)") + F(P-2) and also to the ionic limit CH3+((1)A(1)') + F-(S-1). All curves except the one for the ionic state show repulsive behavior. The search for a global minimum for the ionic state led to the structure H2CH+F- in the 3(1)A' state. It is strongly bound by 5.67 eV with respect to the ionic dissociation limit of F- + CH3+.