A prosthetic heart valve can comprise a radially collapsible and expandable annular frame and a leaflet structure comprising a plurality of leaflets mounted within the frame. The frame can have commissure attachment portions that are configured to support the commissures of the leaflets in unique ways. For example, commissure attachment portions can include at least two struts defining a gap therebetween. Additionally, angularly-spaced commissure attachment portions can comprise inner struts and outer struts. Adjacent side portions of leaflets can extend through a gap between the inner struts of a corresponding commissure attachment portion. Further features and arrangements are also possible.