Performance in consistent arithmetical word problems was assessed in 941 pupils aged eight (N = 415), ten (N = 274), and thirteen (N = 252) classified in four achievement groups by standardised achievement tests: low achievement in both mathematics and reading (MLRL), in mathematics only (ML-only), in reading only (RL-only), and normal achievement in both (NA). Both the MLRL and ML-only groups performed below the two other groups. On the easiest tasks at the lowest age levels the MLRL-group displayed weaker results than the ML-only group, otherwise they performed at the same level. The RL-only pupils performed at the same level as the NA-group at age 8 and 10, but below the NA-group at age 13. The findings can indicate that reading ability does not interfere with the performance on the word problems as much as general mathematical ability.