Context :

Aims : We aim to study the structure of the nebula around the post-AGB , binary star 89 Her .
The presence of a rotating disk around this star had been proposed but not been yet confirmed by observations .

Methods : We present high-resolution PdBI maps of CO J =2–1 and 1–0 .
Properties of the nebula are directly derived from the data and model fitting .
We also present N-band interferometric data on the extent of the hot dust emission , obtained with the VLTI .

Results : Two nebular components are found : ( a ) an extended hour-glass-like structure , with expansion velocities of \sim 7 km s ^ { -1 } and a total mass \sim 3 10 ^ { -3 } M _ { \mbox { \sun } } , and ( b ) an unresolved very compact component , smaller than \sim 0 \aas@@fstack { \prime \prime } 4 and with a low total velocity dispersion of \sim 5 km s ^ { -1 } .
We can not determine the velocity field in the compact component , but we argue that it can hardly be in expansion , since this would require too recent and too sudden an ejection of mass .
On the other hand , assuming that this component is a keplerian disk , we derive disk properties that are compatible with expectations for such a structure ; in particular , the size of the rotating gas disk should be very similar to the extent of the hot dust component from our VLTI data .
Assuming that the equator of the extended nebula coincides with the binary orbital plane , we provide new results on the companion star mass and orbit .

Conclusions :