At present, the use of strained silicon in the design of high performance devices has been shown to be very successful. However, even if the method has found wide application many open questions still persist. A lot of interesting aspects in conjunction with the influence of dopant atoms on the elastic properties of silicon have not yet been fully understood or even studied. The influence of phosphorus and boron doping on the elastic properties of silicon is studied by means of the perturbed angular correlation (PAC) method using the acceptor 111In as probe. It was found that the response of the silicon lattice to mechanical stress showed strong differences depending on the dopant species. Doping with donors leads to a significant reduction of the elastic constants of silicon whereas acceptors do not have any influence on them.