During Dec. 2-4, 2001, the comet C/2000 WM1 (LINEAR) was observed at ESO by using the 1.5m Danish Telescope equipped with DFOSC as focal plane. The comet was imaged in broad-band filters (R,I) and interferometric filters covering the CN, C2, C3 gas emissions as well as clear continuum regions. Additionally, long-slit spectra were also taken as part of an exhaustive observational campaign in the optical, near IR and thermal IR. This paper presents the morphological analysis of the coma, study of the dust in terms of brightness profiles and in the frame of Afρ, analysis of the gaseous to derive production rates and species scale lengths. These results show that regarding the gas coma, C/2000 WM1 did not show any abnormal behaviour prior perihelion: (I) no clear gas structures as jets, shells or spikes are present, (II) the deduced Haser scale lengths are within reported ranges for other comets, (III) CN, C2 and C3 production rates at τH ~ 1.72 AU are (1.56±0.7)×1026, (3.72±0.21)×1026 and (5.45±0.13)×1024 s-1, respectively. On the other hand, the study of the dust coma reveals that variations in the size and/or composition of the grains might be occurring while travelling outwards. This fact is manifested as a sharp decrease of ΣAf vs ρ at 700 ≤ ρ ≤ 15000 km. This same behaviour is seen when analysing the near IR and IR images obtained during the same observing run.