A series of isochromeno[4,3-c]pyrazole-5(1H)-one derivatives 7b–h were prepared and tested at 10 μM for their ability to displace specific [3H]flunitrazepam from bovine brain membranes. The substitution pattern of the above derivatives was shown to influence the receptor affinity. The most active compound of the series was 7e, showing a 54% inhibition of [3H]flunitrazepam binding. Compounds 7a–d,i