The wide diffusion of Bt-cotton in China (mainland) is well documented. It is estimated that Bt-cotton covers about 70% of the national cotton areas. Cotton is produced in three regions: Yellow River Valley, Yangtze River Valley and Xinjiang Province located in the North-West of the country. In the last province, pest pressure is low and there is little rationale for using Bt-cotton. This type of cotton is therefore mainly grown in the Yellow and Yangtze River Valleys. This paper provides evidence of the large-scale diffusion of Bt-cotton in the Yangtze River Valley (far less addressed in papers accessible to the international community). It confirms that, in this region, the specific advantages of Bt-cotton are of limited extent, if any, as already reported by Chinese scholars. This is a case of paradox which has not been reported earlier. The paper is based on official data series which have seldom been exploited, in particular data related to cotton areas distributed between the main varieties and to registration for variety marketing on a national scale. Our paper suggests two factors to explain the observed paradox. We first contend that Btcotton diffusion has benefited from synergy with pre-existing production techniques, namely transplanting with hybrid seeds, a phenomenon we call technological integration. This integration has also been enhanced by remarkable development of the variety and seed sectors, which has literally embedded technological integration in hybrid seeds. The concept of technological integration might be more general than in the studied case and brings into question the practice of Bt-cotton seed pricing.