Disclosed are pyridazine compounds of the formula I which are useful for inhibiting glycogen synthase kinase 3 (GSK-3), methods of making the compounds, compositions containing the compounds, and methods of treatment using the compounds: In formula I indicates a single bond or a double bond; X is O, S or N—R5; R1, R2 are independently selected from the group consisting of H, NH2, NH—C1-C6-alkyl, OH, ═O, (i.e. a carbonyl group), C1-C6-alkoxy, halogen, methyl, C2-C4-alkyl, C3-C4-cycloalkyl, C3-C4-alkenyl, fluorinated C1-C4-alkyl, fluorinated C3-C4-cycloalkyl, fluorinated C3-C4-alkenyl, formyl, C1-C3-alkylcarbonyl, and an aromatic radical Ar, R1 and R2 together with the carbon atoms, to which they are attached, form a fused, saturated or unsaturated 5-, 6- or 7-membered C-bound carbocyclic or heterocyclic ring comprising 1 heteroatom, selected from nitrogen, oxygen and sulfur as ring member and 0, 1 or 2 further heteroatoms, independently selected from O, S and N, as ring members, wherein the fused ring is unsubstituted or may carry 1, 2 or 3 substituents selected, independently of each other, from the group of radicals R4 as defined below; R3 is hydrogen OH, halogen, CN, nitro, C1-C6-alkyl, fluorinated C1-C6-alkyl, C1-C6-hydroxyalkyl, C1-C6-alkoxy-C1-C6-alkyl, C2-C6-alkenyl, fluorinated C2-C6-alkenyl, C2-C6-alkynyl, C3-C7-cycloalkyl, fluorinated C3-C7-cycloalkyl, C1-C6-alkoxy, C1-C6-hydroxyalkoxy, C1-C6-alkoxy-C1-C6-alkoxy, fluorinated C1-C6-alkoxy, C1-C6-alkylthio, fluorinated C1-C6-alkylthio, C1-C6-alkylsulfinyl, fluorinated C1-C6-alkylsulfinyl, C1-C6-alkylsulfonyl, fluorinated C1-C6-alkylsulfonyl, C1-C6-alkylcarbonyl, fluorinated C1-C6-alkylcarbonyl, C1-C6-alkylcarbonylamino, fluorinated C1-C6-alkylcarbonylamino, carboxy, C1-C6-alkyloxycarbonyl, fluorinated C1-C6-alkoxycarbonyl, NRaRb, C(O)—NReRf, NH—C(O)—NReRf, NRaRb—C1-C6-alkylene, O—NRaRb, etc. and wherein R4 and R5 are as defined in the specification and the claims.