There is a discrepancy between the observed and predicted numbers of Galactic supernova remnants (SNRs), likely due to observational biases that hinder the detection of old, faint, large remnants, as well as very young, small remnants, caused by poor sensitivity and spatial resolution. The goal of this thesis is to address this issue and explore missing SNRs. As a first step, distances to 29 SNRs and one SNR candidate were estimated using HI absorption and 13CO emission spectra from various surveys, leading to improved distance estimates compared to previous values. Using the THOR survey, two compact young SNRs, G18.760-0.072 and G31.299-0:0493, were identified at distances of 4.7 ± 0.2 kpc and 5.0 ± 0.3 kpc respectively. Additionally, a table of 227 extragalactic sources is presented. The detection of these SNRs is consistent with the THOR sensitivity limit and the distribution of integrated flux densities of SNRs. To determine the radial distribution and estimate the total number of SNRs in the Galaxy, distances to 215 SNRs were compiled using a consistent rotation curve. Two methods were employed: applying correction factors for selection effects and comparing functional forms against the data. I calculated that the total count of SNRs in the Galaxy ranges roughly between 2400 and 5600. Statistical analyses were performed on a sample of 390 SNRs, investigating their diameters, ages, spectral indices, Galactic heights, and spherical symmetries. The accuracy of distance estimation using the Σ-D relation was also examined. The average diameter of Galactic SNRs was determined to be 30.5 pc, with a standard error of 1.7 pc and a standard deviation of 25.4 pc. The geometric mean diameter was found to be 21.9 pc, with a geometric standard deviation factor of 2.4. This suggests that, on average, the sizes of Galactic SNRs are smaller when compared to those observed in other galaxies. Age estimates were obtained for 97 SNRs, revealing a supernova birth rate slightly lower than currently accepted values but within 2σ of those values. The mean spectral index of shell-type SNRs was determined to be -0:51 ± 0:01. No significant correlations were observed between spectral indices and other SNR parameters. The distribution of SNRs with respect to Galactic height was best described by an exponential distribution with a scale height of 48 ± 4 pc. While there is evidence of a large number of unidentified SNRs, their detection remains challenging due to their concentration near the Galactic plane, foreground objects, and the bright Galactic synchrotron background. The current lack of large-scale spiral structure in the SNR distribution may change with the addition of several hundred more SNRs, offering new insights into their distribution
