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Cannabis sativa is the most highly demanded illegal drug in the world, even more than amphetamines, cocaine and opiates. In Brazil, one of the strategies to reduce its consumption is the identification and destruction of cultivation. Plantations are identified visually by experienced Brazilian Federal Police agents using helicopters. This study analyzed the potential of the NDVI (Normalized Difference Vegetation Index) derived from temporal series of the SPOT-5 HRG (High Resolution Geometric) images to detect plantations of Cannabis surrounded by the Caatinga vegetation in the semi-arid region of Pernambuco State. Absolute values and multitemporal series of NDVI from two sites used to plant Cannabis and from surrounding natural vegetation were analyzed to find anomalies related to the presence of such plantations. Results showed a strong seasonality of Caatinga phytophysiognomies and heterogeneous spectral pattern of Cannabis sativa. In some cases, Cannabis plantations presented growing patterns higher than the Caatinga vegetation, as a consequence of water and fertilizer supplies; in other, an abrupt decrease of NDVI values, as a consequence of field management practices - soil preparation and harvesting - or destruction. The analysis of dynamics of NDVI allowed detecting Cannabis cultivations from temporal series of SPOT-5 HRG.