The strong gauche preference along with the F-C-C-N+ fragment in 3-fluoropiperidinium cation and analogues, in the gas phase, is dictated by electrostatic interactions, which can be both hydrogen bond F center dot center dot center dot H(N+) and F/N+ attraction. In aqueous solution, where most biochemical processes take place, electrostatic effects are strongly attenuated and hyperconjugation is calculated to be at least competitive with Lewis-type interactions.