Tin oxide (SnO2) nanoparticles have been synthesized by simple route of sol-gel method. Polyaniline-tin oxide (PANI/SnO2) nanocomposite (sample A) was prepared by an in-situ polymerization of aniline in the presence of as-synthesized SnO2 nanoparticles. Similarly, tin oxide-intercalated polyaniline nanocomposite (sample B) was prepared using tin chloride (SnCl4.5H2O) as precursor during polymerization of aniline. Morphology and structure of both the nanocomposites have been studied using XRD pattern, FTIR spectra and SEM images which reveals that SnO2 was uniformly mixed within the PANI matrix. In this paper we report the comparison of polyaniline-tin oxide (PANI/SnO2) nanocomposites sample A and B for the response to ammonia. A laboratory set up for sensing ammonia has been built up using four probe resistivity unit and the response of the prepared PANI/SnO2 nanocomposites to ammonia vapour for different concentration (5, 10, and 15%) was tested. PANI/SnO2 nanocomposites were found to be good materials for NH3 detection even at room temperature as compared to that of pure SnO2. By comparing the response of sample A and B to the ammonia vapour, the sample A was found to be more sensitive than sample B due to highly porosity and surface activity of sample A. The results were reproducible and checked by repeating observations. Synthesis route for the preparation of PANI/SnO2 nanocomposites is an important factor while selecting the materials for ammonia sensing.