Recent investigations aimed at estimating the distance to the young LMC cluster NGC 1866 have made use of Red Clump stars in the surrounding LMC field , together with empirical and theoretical Main-Sequence fitting methods , and have found significantly different distances for the field and the cluster , the latter being closer by in distance modulus by \Delta ( DM ) \sim 0.20 mag .
In this paper we ( re- ) consider the Cepheid star population of NGC 1866 , to try to shed some light on this discrepancy .
By combining various extensive photometric datasets in B , V,I and single-epoch 2mass JHK 
photometry , PL relationships for the cluster Cepheids are obtained .
A comparison between the field LMC and cluster PL relationships for the reddening free Wesenheit index gives a firm determination of the distance between the cluster and the LMC main body ( 0.04 mag in distance modulus , the cluster being more distant ) which , coupled to a model for the geometry of the LMC disk , provides \Delta ( DM ) ranging between 0.0 and - 0.11 mag .
The simultaneous comparison of the PL 
relationships in B , V and I for the cluster and LMC field gives an estimate of the cluster reddening , which results to be E ( B - V ) = 0.12 \pm 0.02 .
This determination is higher than the canonical value of 0.06 mag used in all previous studies , but we show that it is not in contradiction with a re-analysis of independent estimates .
The adoption of the LMC extinction law recently presented by Gordon et al .
( 2003 ) does not change these results .
The cluster Main Sequence fitting distance obtained with this new reddening is DM = 18.58 \pm 
0.08 , fully compatible with the Red Clump value of DM = 18.53 \pm 0.07 ( random ) ^ { +0.02 } _ { -0.05 } ( systematic ) and the Cepheid constraint on \Delta ( DM ) .
Finally , we determined the distance to the cluster by using a Cepheid Wesenheit PL relationship with slope coming from LMC observations , and absolute magnitude zero point calibrated on Hipparcos parallaxes of Galactic Cepheids , in the assumption that the relationship is independent of metallicity ; the resulting DM = 18.65 \pm 0.10 is not an accurate estimate of the LMC distance because of possible metallicity effects but , when compared to the revised Main Sequence fitting value , it points out to a possibly weak dependence of the Wesenheit PL relationship on the Cepheid chemical composition , at least in the period range between 2.5 and 3.5 days .