  In a recent paper describing HST observations of Cepheids in the spiral
galaxy NGC 4258, Newman et al. (2001) report that the revised calibrations and
methods for the Key Project on the Extragalactic Distance Scale yield that the
true distance modulus of this galaxy is 29.40+-0.09 mag, corresponding to a
metric distance of 7.6+-0.3 Mpc. This Cepheid distance, which holds for 18.50
mag as the true distance modulus of the LMC, is not significantly larger than
7.2+-0.5 Mpc, the value determined by Herrnstein et al. (1999) from purely
geometric considerations on the orbital motions of water maser sources.
However, if the metallicity difference D[O/H]~0.35 between NGC 4258 and LMC is
taken into account, then the Key Project methods lead to a
metallicity-corrected value of 29.47+-0.09 mag, with 18.50 mag for the LMC,
namely to a Cepheid distance of 7.8+-0.3 Mpc, which is 1.2 sigma from the maser
determination. In this paper we show that the metallicity correction on Cepheid
distance determinations, as suggested by pulsation models, might provide the
natural way of reaching a close agreement between Cepheid and maser distance to
NGC 4258 for a wide variety of LMC distance determinations.
