Landscape chamcteristics such as small patch size and landcover heterogeneity have been hypothesized to increase the likelihood of mis-classifying pixels during thematic image classification. However, there has been a lack of empirical evidence to support these hypotheses. This study utilizes data gathered as part of the accuracy assessment of the 1992 National Land Cover Data (NLCD) set to identify and quantify the impacts of land-cover heterogeneity and patch size on classification accuracy Logistic regression is employed to assess the impacts of these variables, as well as the impact of land-cover class information. The results reveal that accuracy decreases as landcover heterogeneity increases and as patch size decreases. These landscape variables remain significant factors in explaining classification accuracy even when adjusted for their confounding association with land-cover class information.