We examined whether fluid intelligence (Gf) is better predicted by the storage capacity of active memory or by the effectiveness of executive control. In two psychometric studies, we measured storage capacity with three kinds of task which required the maintenance of a visual array, the monitoring of simple relations among perceptually available stimuli, or the quick update of information. Executive control was measured with tasks reflecting three executive functions, namely attention control, interference resolution, and response inhibition. Using structural equation modeling, we found that all storage tasks loaded on one latent variable, which predicted on average 70% of variance in Gf (Studies 1 and 2). On the contrary, neither interference resolution nor response inhibition was substantially related to Gf or to any other variable (Study 1). Although attention control predicted on average 25% of Gf variance (Studies 1 and 2), when storage capacity was statistically controlled for, attention control no longer significantly explained Gf. (Contains 5 tables and 6 figures.)