This paper presents the first results from a study of multi-temporal JERS repeat pass coherence. Two test areas in a forest region north of Krasnoyarsk in Siberia have been used to investigate if L-band coherence with a 44-day temporal baseline can be used for estimations of growing stock volume in boreal forest. The available data show promising results for winter images, but for the summer scenes the standard deviations are too large to give reliable results. A comparison with ERS tandem coherence has also been done.