The results of the paper of Prof. Tan “An improved response spectrum method for non-classically damped systems”, previously published in Bulletin of Earthquake Engineering, are analyzed. It is noted that the paper contains important material which allows one to analyze systems with arbitrary damping. According to the authors, the method of constructing the velocity spectra of damped systems is important for calculating damped systems. The material presented in the paper is a kind of basis for explicitly taking damping into account in regulatory documents. To do this, it is necessary to link the existing regulatory documents with theoretical studies. Relevant proposals are set out in the presented response and are illustrated by an example. At present the most difficult thing is to carefully construct damping equations, in particular, to take account of internal friction in the material