The objective of the present study was to investigate the influence of the single nucleotide polymorphism (rs17238540) at the 3-hydroxy-3-methylglutaryl-coenzyme A reductase gene (HMGCR) on the relationship between serum lipids and dietary fat and fibre (NSP). FFQ and pyrosequencing were used to assess cross-sectional dietary intake and HMGCR genotype in a population study with data for serum lipids available. Genotype frequencies and allele distributions for 23 011 participants were: TT 95.65 %, TG 4.29 % and GG 0.06 %; T 97.8 % and G 2.2 %. In regression analyses, the TG+GG group showed a significant positive relationship between TAG and SFA intake (+0.11 (95 % CI 0.02, 0.20) mmol TAG/l; P = 0.017; per 3 % SFA energy increase) while the TT individuals showed no change in the TAG levels related to SFA intake ( - 0.0007 (95 % CI - 0.02, 0.02) mmol TAG/l; P = 0.99). TG+GG individuals showed an inverse relationship between TAG and fibre intake higher ( - 0.14 (95 % CI - 0.22, - 0.05) mmol TAG/l than the TT group ( - 0.04 (95 % CI - 0.06, - 0.02) mmol TAG/l). In both cases the respective coefficient regressions of TAG were different between the genotype groups (Z = 2.27, P = 0.023 for SFA intake; Z = 2.19, P = 0.029 for fibre intake). Individuals carrying the G allele may show a greater response in lower TAG levels with reduced SFA intake and increased fibre intake compared with those homozygous for the T allele. The effectiveness of different dietary interventions to control serum lipids may vary according to HMGCR genotype.