The use of CO2 as a dry-cleaning solvent for old silk textiles was investigated. The cleaning procedures under study were tested on the 18th century religious garments from Virgin and Child from Palácio das Necessidades, Lisbon. The effect of using different cleaning solvent streams, supercritical and liquid CO2, CO2 + isopropanol and CO2 + isopropanol + water, was evaluated concerning the dirt particles extracted, weight loss and colour variation of the scapulary samples tested. Particularly, the use of liquid CO2 and the addition of water as a co-solvent had a strong positive effect on removal of dirt particles. CO2-assisted cleaning proved to be a very safe method for the cleaning of very deteriorated silk textiles. The fibres and the textile structure were not physically damaged and the method did not promote the loss of material, which is an enormous advantage for the cleaning of textiles of historic or artistic value.