A seismic wave attenuation study was performed for volcano-tectonic earthquakes at Puracé volcano (PV), Colombia, for the period of 2006-2015 by using the inverse of coda Q (Q-1) of coda waves. A total of 310 high-quality earthquakes were used for the analysis. The results showed low Q values for PV suggesting high attenuation in this region. Additionally, Q values were related to Vp/Vs data to calculate Qp −1/Qs −1 ratios. Low Qp −1/Qs −1 ratios were found, and they were associated with fluids predominantly in the liquid phase rather than in the gaseous phase located at shallow parts of the PV, which affected the hydrothermal system producing LP and “Tornillo”-type volcano earthquakes. It is inferred that the recent activity of PV is driven by the hydrothermal system, with a small influence from the magmatic system.  The Qp −1/Qs −1 ratio can be used as a marker for changes in gas content in the hydrothermal system, becoming a useful tool for routine monitoring tasks at PV.