Intra-thallus variation in fatty acid and pigment contents and profiles was investigated in five species of Laminariales (Alaria esculenta, Laminaria digitata, Laminaria hyperborea, Saccharina latissima, and Saccorhiza polyschides), and three Fucales (Ascophyllum nodosum, Fucus serratus, and Himanthalia elongata). Significant variation occurred across all species and compounds examined. Total fatty acids were generally higher in the fronds, with highest levels and largest variability observed in A. nodosum (1.5% of dry weight (DW) in the base, 6.3% of DW in frond tips). Percentages of the omega-3 fatty acids 18:4 n-3 and 20:5 n-3 were generally higher in more distal parts, while 20:4 n-6 exhibited a contrasting pattern, with higher levels in basal structures and holdfasts. Trends for pigments were similar to those for fatty acids in Laminariales. In the Fucales, highest levels were detected in the mid-fronds, with lower concentrations in meristematic areas. Highest levels and greatest variability in pigments (e.g., chl a) was observed in F. serratus (1.07 mg · g(-1) DW in the base, 3.04 mg · g(-1) DW in the mid frond). Intra-thallus variability was attributed to physiological functions of the respective thallus sections, e.g., photosynthetic activity, meristematic tissue, and to variations in physical attributes of the structures investigated. Regarding potential commercial nutritional applications, fronds appeared to represent most suitable source materials, due to higher levels of pigments, polyunsaturated fatty acids, and more preferable omega-3/omega-6 ratios.