Ritz vectors are parameters, which describe object dynamics in similar way as modal vectors. Their advantage with respect to modal vectors is a fact, that less number of them is required to estimate object response. It is also proofed, that Ritz vectors are more sensitive for damage detection then modal vectors. The problem which arises, when one wants to use Ritz vectors for damage assessment is that there are no many methods to extract Ritz vectors from operational data. In addition, the methods require knowledge of analytical mass matrix or state a space model matrix, which makes them rather complicated. In the paper two Ritz vectors extraction methods are taken into account. First bases on flexibility matrix and second is related with state space model. Both of them are evaluated with respect to analytical procedure of Ritz vectors calculation. For the vectors evaluation, a simulation data from theoretical model were used. In next step Ritz vectors were extracted from data measured on a real structure. On the structure damage was simulated. The Ritz vectors extracted with use of both tested methods were used to detect damage.