The purpose of this study is to analyze the clinicopathological features and radiographic image qualities of 210 cases of gastric cancers (GC), which were judged as category-3b (Cat-3b GCs) as compared to the 88 cases of GC judged as Cat-4 or 5 (Cat-4/5 GCs) based on the Categorized criteria for X-rays image reading of the population-based gastric cancer screening in 2015 fiscal year radiographic screening program conducted by Miyagi Cancer Society. The detection rate of early GC of Cat-3b GCs was 83.8%, which was a significantly higher rate than 64.8% of Cat-4/5 GCs. In addition, the well-differentiated early GC with depressed features or the lesions less than 20 mm in diameter were frequently included in Cat-3b GCs for a comparison with the Cat-4/5 GCs. However, GCs more than 21 mm in diameter and advanced GCs were also included in Cat-3b GCs because of unsatisfactory photographic technique and low image quality. Of 210 Cat-3b GCs, a certain presence of the lesion was identified in 86 cases (41.0%) because a whole image of the lesion was available by a good radiographic contrast. The frequency of Cat-3b GCs with a good depiction increased in early-stage GCs with submucosal invasion and more frequently in advanced stage cancers. The number of additional photographing of the lesion was 2.1±1.6 (mean±S. D. ) in Cat-3b GCs, whereas it was 3.5±1.9 in Cat-4/5 GCs, which were discovered from the examinees judged as Cat-4 or 5 by the radiographic screening. The former number of additional photographing of the lesion was significantly lower than the latter (p < 0.001). On the contrary, 124 cases (59.0%) showed a poor radiographic contrast and were then incapable of the diagnosis of gastric cancer. An insufficient spreading of barium led to such poor depiction. These data suggested the necessity of further skill-up of photographic technique and improvement of radiographic image quality for diagnostic amelioration of Cat-3b GCs.