We present high-angular resolution observations of the circumstellar disk around the massive Herbig Be star R Mon ( M _ { * } \sim 8 M _ { \odot } ) in the continuum at 2.7mm and 1.3mm and the ^ { 12 } CO 1 \rightarrow 0 and 2 \rightarrow 1 rotational lines .
Based on the new 1.3mm continuum image we estimate a disk mass ( gas+dust ) of 0.007 M _ { \odot } and an outer radius of < 150 AU .
Our CO images are consistent with the existence of a Keplerian rotating gaseous disk around this star .
Up to our knowledge , this is the most clear evidence for the existence of Keplerian disks around massive stars reported thus far .
The mass and physical characteristics of this disk are similar to those of the more evolved T Tauri stars and indicate a shorter timescale for the evolution and dispersal of circumstellar disks around massive stars which lose most of their mass before the star becomes visible .