The purpose of this work was the investigation of behaviour of three Polish CaO-based sorbents during calcium looping cycles. All investigations were conducted with a Netzsch STA 409PG Luxx thermogravimetric analyser. Samples weighing ms = 10.0(1) mg were placed in an Al2O3 crucible. The calcium looping processes were performed at two carbonation temperatures (650°C and 680°C) and three calcination temperatures (880°, 900° and 920°C). Additionally, calcination-carbonation cycles with different gas flows were explored. We investigated the influence of CO₂ concentration and total gas flow on carbonation conversion.