Since 2004, the satellite-borne Ozone Mapping Instrument (OMI) has observed sulphur dioxide (SO$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$) plumes during both quiescence and effusive eruptive activity at Soufrière Hills Volcano, Montserrat. On average, OMI detected a SO$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ plume 4–6 times more frequently during effusive periods than during quiescence in the 2008–2010 period. The increased ability of OMI to detect SO$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ during eruptive periods is mainly due to an increase in plume altitude rather than a higher SO$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ emission rate. Three styles of eruptive activity cause thermal lofting of gases (Vulcanian explosions; pyroclastic flows; a hot lava dome) and the resultant plume altitudes are estimated from observations and models. Most lofting plumes from Soufrière Hills are derived from hot domes and pyroclastic flows. Although Vulcanian explosions produced the largest plumes, some produced only negligible SO$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ signals detected by OMI. OMI is most valuable for monitoring purposes at this volcano during periods of lava dome growth and during explosive activity.