The dust and plasma tails of Comet Wilson 1987VII were studied using photographic plates obtained by means of an ESO Schmidt camera. The plates were digitized adopting a square scanning window of 50 microns and properly calibrated by means of calibration wedges. Dust grains of diameters between 10 microns and 5 cm, ejected during the time interval -600 less than t less than -30 (days related to perihelion), were considered and a total dust mass of (4 + or - 2) x 10 to the 14th g was obtained, together with a power index of the time-averaged size distribution of -3.0 + or - 0.1. The high value of the power index of the time-averaged size distribution with respect to the lower value of old comets might point out intrinsic differences and suggest new formations. 6 refs.