  Data on HII regions, molecular clouds, and methanol masers have been used to
estimate the Sun's distance from the symmetry plane zo and the vertical disk
scale height h. Kinematic distance estimates are available for all objects in
these samples. The Local-arm (Orion-arm) objects are shown to affect noticeably
the pattern of the z distribution. The deviations from the distribution
symmetry are particularly pronounced for the sample of masers with measured
trigonometric parallaxes, where the fraction of Local-arm masers is large. The
situation with the sample of HII regions in the solar neighborhood is similar.
We have concluded that it is better to exclude the Local arm from
consideration. Based on the model of a self-gravitating isothermal disk, we
have obtained the following estimates from objects located in the inner region
of the Galaxy (R<= Ro): zo= -5.7+/-0.5 pc and h2=24.1+/-0.9 pc from the sample
of 639 methanol masers, zo=-7.6+/-0.4 pc and h2=28.6+/-0.5 pc from 878 HII
regions, zo=-10.1+/-0.5 pc and h2=28.2+/-0.6 pc from 538 giant molecular
clouds.
