AbstractAims  Women with gestational diabetes are more likely to develop Type 2 diabetes and cardiovascular disease after pregnancy; however, the exact nature of the lipid alterations present is not clear. In Mediterranean women with gestational diabetes, we measured low‐density lipoprotein (LDL) size and all seven subclasses, as well as the ‘atherogenic–lipoprotein phenotype’[ALP, e.g. concomitant presence of elevated triglycerides, reduced high‐density lipoprotein (HDL)‐cholesterol and increased small, dense LDL].Methods  In 27 women with gestational diabetes and 23 healthy pregnant women matched for age, weeks of gestation and body mass index, we measured plasma lipids and LDL size and subclasses by gradient gel electrophoresis between 24 and 28 weeks of gestation.Results  Although no significant differences were found in the concentrations of any of the plasma lipids, compared with control subjects women with gestational diabetes had lower LDL size (P = 0.0007) due to reduced LDL‐I (P = 0.0074) and increased LDL‐IVA (P = 0.0146) and ‐IVB (P < 0.0001) subclasses. Correlation analysis revealed that fasting glucose, homeostasis model assessment and glycated haemoglobin were inversely correlated with LDL‐I and positively with LDL‐IVA and ‐IVB (all P < 0.05). ALP due to high HDL‐cholesterol levels was not seen in either group, whereas elevated small, dense LDL were more common in women with gestational diabetes than control subjects (33% vs. 4%, P = 0.0107).Conclusions  Increased levels of small, dense LDL are common in Mediterranean women with gestational diabetes. Whether these findings affect the atherogenic process and clinical end‐points in these women remains to be determined by future prospective studies.