We calculate the critical temperature Tc of a wide range of diborides which have the same crystal structure as MgB2. Their electronic structure is also calculated in the framework of the local density approximation method of density functional theory by using the pseudopotential plane wave approach. The Hopfield factors η of these materials are calculated by the frozen phonon method. Our results show that most of these diborides have low η, and hence low or no Tc; this is consistent with experimental observations. The most important result of our calculation is that AgB2 and AuB2 have higher Tc than MgB2. The high Tc of these two materials comes from the combination of the high density of states and high deformation potential of the σ bands.