Background. Feature and conjunction search tasks are widely used to study attentional deployment in space and in time. However, the spatiotemporal behavior of attention in these tasks remains under debate. Are multiple search stimuli processed in parallel or sequentially? Does this differ between these two types of search? If so, how? We used an innovative methodology to estimate the distribution of attention on a single trial basis for feature and conjunction search. Methods. Observers (n=8) performed feature and conjunction search tasks during separate sessions. They had to detect and discriminate a tilted low spatial-frequency grating among 3 similar looking distractors (i.e., vertical gratings in feature, and vertical or high spatial-frequency tilted gratings in conjunction search). After a variable delay, two additional probes (Landolt C’s) were flashed at random locations. Performance in reporting the probes was used to infer attention deployment to those locations. Using the approach developed by Dugué et al. (PNAS 2015), we determined the probability of probe report at the most (P1) and least (P2) attended locations on a given trial. Were P1 and P2 equal, we would conclude that attention was uniformly distributed across the four locations occupied by the search stimuli. Otherwise, we would conclude that attention was non-uniformly distributed across the four locations. Results/Interpretations. Our results show that, for both feature and conjunction search, attention was non-uniformly distributed across the four locations. These results rule out a strict parallel/uniform model of attention processing during both the feature and conjunction search tasks. Interestingly, attentional distribution over time depended on the location of the probed stimuli in the visual field. This suggests that attentional distribution is heterogeneous across isoeccentric locations in a manner resembling asymmetries in visual performance at these locations. Acknowledgement: This work was supported by: NIH (RO1-EY016200) to MC and the FYSSEN Foundation to LD.