Magnetic and structural properties of RCo12-xTix with R = Y and Sm and YFe12-xTix compounds have been investigated by using x-ray diffraction and magnetic measurements. It was found that all compounds investigated are almost single phase with the ThMn12-type structure. X-ray diffraction patterns of magnetically aligned powder samples indicate that the easy magnetization directions (EMD) at room temperature are in the basal plane for SmCo12-xTix compounds while for YCo12-xTix and YFe12-xTix compounds the EMDs are along the c-axis. The lattice parameters increase monotonically with increasing Ti content for all the compounds investigated. The Curie temperature TC decreases monotonically with increasing Ti content for both YCo12-xTix and SmCo12-xTix, while TC of YFe12-xTix is almost independent of Ti content. The saturation magnetization Ms decreases with increasing Ti content for all the three systems. The anisotropy field Ba of YCo12-xTix and YFe12-xTix compounds decreases monotonically with increasing Ti content, while the Ti content dependence of the anisotropy fields Ba for SmCo12-xTix compounds at 1.5 K exhibits a maximum at about x = 1.7, which can be understood in terms of a two-sublattice model of anisotropy.