This paper experimentally investigates the particle concentration distribution and deposition in three-dimensional 90 degrees bends considering three potential influencing factors: inlet mass concentration C-m, Reynolds number Re and wall material. Particle penetrations were found to decrease moderately within 11% with the increase of C-m under current conditions, but deposition velocity would increase by 1.29-2.87 times. The inlet particle concentration will not affect the outlet concentration distribution and particle penetration for the particles of St=5.15 x 10(-4). For larger particles, however, higher C-m, St and Re cause higher concentration near the outer wall of bend outlet, lower concentration near the inner wall and even 'particle free zone'. For the outlet concentration distribution, apexes and concave points are observed, which may be formed by the rebounding particles. Furthermore, concentration polarization factor is introduced to analyze the outlet nonuniformity. Accordingly, Re is found to be a higher weighting factor compared with C-m. Compared to penetration, deposition velocity is more sensitive to wall materials, for example, with an increase factor up to 1.45. Furthermore, a rough estimation method and an empirical model are suggested to establish the correlation among dimensionless outlet concentration, St and 'particle free zone'. (c) 2013 Elsevier Ltd. All rights reserved.