The out-of-plane compressive properties of foam materials are essential for their performance as core material in sandwich structures. Accurate data for these properties are crucial for modeling and analysis of impact response and critical design assessment of e.g. sandwich structures. Current standards differ in specifying how the strains should be measured. When different standard methods are used, significant differences in test results for flatwise compression are obtained. An experimental study of the out-of-plane compressive properties (strength and modulus) of foam materials is conducted, where two types of foams are studied; Rohacell 200 Hero and Divinycell H60. Both are closed cell structured foams used for cores in sandwich materials. A review of established test methodologies is conducted and the test results show that there is a significant difference in strain values measured from the cross head displacement (termed "gross core strain") and when extensometer directly applied onto the foam (termed "net core strain"). The results are not related to the compliance of the test rig, which is another issue outside the scope of this investigation. The effect of surface priming on the compressive behavior is further investigated followed by digital image correlation (DIC) for detailed recordings of the strain fields.