This thesis presents an analysis of excited states of B0, B+ and B0 s mesons, decaying to B mesons while emitting a pion or kaon. They are reconstructed from their decay products and a selection is performed to discard wrongly reconstructed B(s) mesons with the multivariate analysis software NeuroBayes, as described in chapter 5. In the training process, the sPlot method and measured and simulated data are used. Chapter 6 describes how the properties of excited B(s) are determined by an unbinned maximum likelihood t to their mass spectra. The systematic uncertainties determined in this analysis are described in chapter 7. The results of this thesis are presented in chapter 8 and a conclusion is given in chapter 9. The results shown in this thesis have been published before in [1].