In the present study on the development of new anticonvulsants, twenty new 6-methyl-1-substituted-4,6-diazaspiro[2.4]heptane-5,7-diones were synthesized and tested for anticonvulsant activity using the maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) screens. Their neurotoxicity was determined by the rotorod test. In this series, all of the alkyl- and aryl-substituted 5,5-cyclopropanespirohydantoins showed more or less protection against MES and/or scPTZ models. The most active of the series was 6-methyl-1-(4-(methylsulfonyl)phenyl)-4,6-diazaspiro[2.4]heptane-5,7-dione (6 t), which showed a MES ED(50) value of 12.5 mg/kg in mice. The median toxic dose (TD(50)) was 310 mg/kg, providing compound 6 t with a protection index (PI = TD(50)/ED(50)) of 24.8 in the MES test which is better than phenytoin.