Methods are presented for assessing minimum errors and cloud inhomogeneity effects in cloud liquid water path (LWP) products derived from passive microwave satellite measurements. Using coincident visible/infrared satellite data, errors are isolated by identifying certain cloud conditions within the microwave sensor's field of view. Analysis of 3 weeks of global pixel-level LWP data revealed that 70% of the systematic errors occurred between −0.011 and +0.025 kgm−2, with the mean random error being 0.013 kgm−2. For overcast clouds these systematic errors translate to a mean lower-bound relative error of about +23%. A significant correlation of these products with near-surface wind speed was also shown. The LWP products were found to depend on cloud fraction as well, suggesting the influence of beam filling errors. This approach shows promise in characterizing the minimum errors in LWP products needed for climate and remote sensing studies as well as future data assimilation applications.