The aim of this work was to evaluate the effect of potassium and magnesium treatment on physicochemical and rheological properties of native potato, corn, and spelt starches. Treatment of starch by one of the metals resulted in an increase in the amount of the used element, with the increase accompanied by decrease in the amount of the other metal. Starches fortified with metal ions did not differ significantly from the native starches in gelatinization characteristics. Effect of metal ions on rheological behavior of starch pastes was the greatest in corn starch with potassium. In the case of the other pastes the effect depended both on type of starch and kind of metal ions. The modified starches formed harder gels than the native starches. Starches treated with potassium ions showed lower rate of retrogradation than the respective native starches. The modified starches were also more susceptible to enzymatic hydrolysis than their native counter- parts. Thermal treatment of native and modified with potassium and magnesium starches led to formation of carbohydrate radicals, which character and amounts depended on the starch origin as well as the kind of metal ions. Spelt starch was the most susceptible to the formation of radicals, whereas the structure of corn starch was the most stable. Effects of metal ions were opposite: potassium ions increased, whereas magnesium ones decreased the amount of radicals in comparison with native spelt starch.