Tree species in tropical dry forests employ a wide range of strategies to cope with seasonal drought including regulation of hydraulic function. However it is uncertain if co-occurring lianas also possess a diversity of strategies. For a taxonomically diverse group of 14 tree and 7 liana species we measured morphological and hydraulic functional traits during an unusual drought and under non-drought conditions to determine (i) if trees have different water-use strategies than lianas and (ii) if relationships among these traits can be used to better understand how tree and liana species regulate diurnal leaf water potential (?diurnal). In this Costa Rican tropical dry forest lianas and trees had overlapping water-use strategies but differed in many leaf economic spectrum traits. Specifically we found that both lianas and trees employed a diversity of ?diurnal regulation strategies which did not differ statistically. However lianas and trees did significantly differ in terms of certain traits including leaf area specific leaf area petiole length wood vessel diameter and xylem vessel density. All liana and tree species we measured fell along a continuum of isohydric (partial) to anisohydric (strict or extreme) ?diurnal regulation strategies and leaf area petiole length stomatal conductance and wood vessel diameter correlated with these strategies. These findings contribute to a trait-based understanding of how plants regulate ?diurnal under both drought stress and sufficient water availability and underscore that lianas and trees employ a similarly wide range of ?diurnal regulation strategies despite having vastly different growth forms.