Toasted-breakfast-cereal is a high quality, high nutritional dry food made of granulated particles. Quality characteristics are important for consumer acceptance and these can be influenced by environmental conditions throughout storage, which can be detrimental for product quality and shelf-life. The aim of this study was to identify the critical quality parameters, determine the influence of environmental conditions on quality parameters and study if the presence of fruit affected the cereals. Toasted-breakfast-cereal was stored according to a mixed full factorial experimental design with two and three levels (20ºC, 30ºC and 40ºC; 33%, 55% and 75; without fruit and with fruit) at three factors (temperature T (°C), relative humidity RH (%) and presence of fruit) to measure the effect of these factors on the quality of cereal. Cereal samples with and without fruit were placed in air-tight containers, above saturated salt solutions individually stored at constant temperatures. Moisture content; water activity; firmness and colour (L-, a- and b-values; browning index and Delta E) were evaluated (at least in triplicate), under the different conditions throughout storage. Statistical analysis of the quality parameters was performed using ANOVA, the Taguchi method and correlations. Moisture content and water activity were found to be the critical quality parameters during storage. Relative humidity is the environmental factor studied that had the greatest effect on the critical quality parameters. The presence of fruit exhibited a significant effect on the critical quality parameters, resulting in a product with lower moisture content. Knowledge of how the environmental conditions affect the critical quality parameters during storage can help the selection of appropriate packaging materials, and facilitate the design of an optimum package to guarantee high quality product during the desired shelf life. Therefore, a package with good barrier properties to water would be recommended for storage of toasted-breakfast-cereal with and without fruit.