ABSTRACT. A series of experiments has been conducted in JET-ILW to investigate the low performance (with H98 < 0.8) of the H-modes plasmas at high triangularity, mainly due to increased pedestal degradation at high density. The study includes variations of the core shape and the divertor geometry to explore the impact of recycling and divertor pumping on pedestal parameters and ELM characteristics. Unlike in JET-C, high density H-mode plasmas in JET-ILW, independently of their triangularity, show signs of a very cold and dense neutral cloud in the inner divertor, with the appearance of ‘inverted’ ELMs typically associated to inter ELM partial detachment. This reflects the different divertor recycling patterns associated with the change in wall materials.