Assuming that the decrease in the density of the interplanetary dust follows an exponential distribution both in the transverse and radial direction, we can write n = no Exp(-(h/H)-(r-l/R)), where h is the distance from the ecliptic plane and r the heliocentric distance both expressed in astronomical units (a.u.); then we show that the modulation of the radiance B(90, 0) of the zodiacal light observed at the ecliptic pole defines the parameter H as a function of the inclination angle B between the zodiacal cloud and the ecliptic plane; moreover, the experimental value of the ratio B(90, 0)/B(90, 90) defines the parameter R. It can be deduced that the flatness of the zodiacal cloud, expressed by R/H, is < 5 and that the plane of symmetry of the zodiacal cloud is very close to that of the invariant plane of the solar system (B<2°).