Introduction: Introduction: thickeners are widely used in swallowing disorders, both for diagnosis and to achieve a safe and effective diet. Recently, products composed of gums have been commercialized in the Spanish market in order to improve the organoleptic and physical qualities of thickened foods. Objective: to compare thickening agents of clinical scope marketed in Spain, and to verify their organoleptic and physical characteristics, to be used in the diagnostic procedures and the feeding of patients with dysphagia. Method: the organoleptic (appearance, colour, smell, taste, aftertaste) and physical (solubility, stability) properties of eight thickeners (4 classic starch-based and 4 new gum-based) were assessed in a sample of 44 healthy subjects. In addition, their usefulness in diagnostic tests was studied by mixing them with dyes and water-soluble contrasts. Results and conclusions: new-generation thickeners, based on gums, generally obtain better scores for their physical and organoleptic qualities than conventional thickeners. Starch thickeners are more suitable for diagnostic tests, as gum thickeners present some peculiarities in their mixtures with dyes and contrasts that must be taken into account in diagnostic tests.