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The physicochemical and rheological properties, as well as the structure of frozen-kefir and frozen-yoghurt samples differing in their chemical composition were evaluated. Particularly, the samples were prepared using two different concentrations of fermented milk product (45% and 60%) and two different concentrations of sugar content (10% and 18%). Rheological properties of the samples were evaluated using dynamic analysis and by the determination of the apparent viscosity, at two different temperatures (-4C και 30C). The pH, acidity (expressed as lactic acid concentration %), overrun and melting rate were also determined. Finally, the structure of the samples was studied using a confocal laser scanning microscope. According to the results, the frozen-kefir samples exhibited increased overrun and melting rate, when compared to frozen-yoghurt samples. Frozen-kefir samples were also showed increased values of the elastic modulus (G΄) at -4C and 30C, as well as increased values of the apparent viscosity at -4C, when compared to frozen-yoghurt samples. The values of the tanδ were decreased at the frozen-kefir samples. The frozen-kefir samples were exhibited a more compact structure, when compared to frozen-yoghurt samples. Increasing the percentage of kefir or yoghurt added at the ice cream mixture resulted in reducing pH and increasing acidity. As it concerns sugar concentration, its increase resulted in reducing overrun, G΄ at -4C and apparent viscosity at -4C, as well as increasing melting rate and tanδ at -4C of the frozen-kefir and frozen-yoghurt samples.