In the present work, we synthesized Sm_2O_3 doped SnO_2 in order to prepare a selective acetone sensor with fast response, quick recovery and good repeatability. Pure as well as 2 mol.%, 4 mol.%, 6 mol.% and 8 mol.% Sm_2O_3 doped SnO_2 nanostructured samples were synthesized by using a co-precipitation method. The characterization of the samples was done by thermogravimetric and differential thermo-gravimetric analysis(TG-DTA), X-ray diffraction(XRD), field emission gun-scanning electron microscopy(FEG-SEM), energy dispersive analysis by X-rays(EDAX), high resolution scanning electron microscopy(HR-TEM), selected area X-ray diffraction(SAED), Brunauer-Emmet-Teller(BET) and ultraviolet-visible-near infrared(UV-Vis-NIR) spectroscopy techniques. The gas response studies of liquid petroleum gas, ammonia, ethanol and acetone vapor were carried out. The results showed that Sm doping systematically lowered operating temperature and enhanced the gas response and selectivity for acetone. The response and recovery time for 6 mol.% Sm_2O_3 doped SnO_2 thick film at the operating temperature of 250 °C were 15 and 24 s, respectively. In the present work, we synthesized Sm 2 O 3 doped SnO 2 in order to prepare a selective acetone sensor with fast response, quick recovery and good repeatability. Pure as well as 2 mol.%, 4 mol.%, 6 mol.% And 8 mol. % Characterization of the samples was done by thermogravimetric and differential thermo-gravimetric analysis (TG-DTA), X-ray diffraction (XRD), field emission gun-scanning electron microscopy (FEG-SEM), energy dispersive analysis by X-rays (EDAX), high resolution scanning electron microscopy (HR-TEM), selected area X-ray diffraction (SAED), Brunauer- Emmet-Teller The gas response studies of liquid petroleum gas, ammonia, ethanol and acetone vapor were carried out. The results showed that Sm doping systematically lowered operating temperature and enhanced the gas response and selectivity for acetone. The re sponse and recovery time for 6 mol.% Sm 2 O 3 doped SnO 2 thick film at the operating temperature of 250 ° C were 15 and 24 s, respectively.