The systematic increase of component separation and profile widths with decreasing frequency in pulsars suggests that the radiation at different frequencies is emitted from different altitudes above the polar cap. This concept is known as the radius-to-frequency mapping. According to RFM the observed low-frequency radiation should be generated farther from the neutron star than higher-frequency radiation. We discuss radial locations of the pulsar emission regions using a geometrical method for the estimation of emission altitudes. It is argued that the emission altitude at a given frequency is slightly different for young and old pulsars.