A method to determine solubility and rate of absorption of carbon dioxide (CO2) from head space volume changes in modified atmosphere packages over time was developed, and validated using distilled water. A high correlation (R-2 = 0.975) between the measured solubility and the theoretical solubility was found. The solubility of CO2 increased linearly with the initial partial pressure of CO2. The temperature dependency of the solubility is according to the temperature dependency of Henry's constant. The solubility of CO2 in farmed cod packaged with 60% initial CO2 and degree of filling of 31.2 +/- 1.3% was determined to 1289 ppm, using the developed method. The time to reach 50%, solubility in farmed cod fillets was about 3.5 h. (c) 2007 Elsevier Ltd. All rights reserved.