Possibility of tanbeta measurement in CMS at LHC

The achievable tanbeta determination accuracy for CMS at LHC is presented. Using MSSM H/A->tau tau decay in the associated production process gg->bbH/A the event rates are measured at large tanbeta and the systematic and statistical errors are estimated. Due to sensitivity of the above event rates to tanbeta it is shown that it is possible to determine constraints on tanbeta for a given set of SUSY parameters and uncertainties.